In a nutshell
Google's machine translation is not perfect. In this case it produced an error.
German is not a SVO-language like English. (SVO means Subject, Verb, Object(s) in exactly this order.) German is a V2-language, wich means: Verb at position 2. Everything else can float almost freely through the sentence, which means, that there is no need to put the subject on position 1. Almost any part of speech can stand on position 1, and the subject can stand almost everywhere in the sentence. (Not everything is allowed, there are rules for this too, but they are tricky.)
Another big difference between German and Englisch: German has four grammatical cases, and grammatical functions within a sentence are not defined by positions (like in English), but by those cases.
Mein Vater hat unserem Nachbarn den alten Rasenmäher geliehen.
- Pos 1: mein Vater
You can ask for it with »wer oder was?« (who or what?), which proofs, that it is in nominative case. If no other part of speech is in nominative case too, this must be the subject.
- Pos 2 (+ last pos): hat ... geliehen
This is the verb. The finite part of it (the part, that has to be declined according to the subject), stands at position 2, and the infinite part (which is not declined by number and grammatical person) stands on the last position.
- Pos 3: unserem Nachbarn
ask: »wem?« (to who?) → dative case (Rule of thumb: someone who receives something is always in dative case)
- Pos 4: den alten Rasenmäher
ask: »wen oder was?« (who or what?) → accusative case
(The English question is the same as for nominative case, which is because English has no accusative case. You have to ask in German.)
The subject always appears in nominative case, and if there is only one part of speech in this case, then you already have found the subject. There are sentences where more than one part of speech are in nominative case, like »Dieser Fluss ist die Grenze« (This river is the border), and in such sentence you can argue, that each of both parts of speech can be thought to be the subject, with is no problem, because this can only happen with verbs that describe that something is equal.
You can rearrange those parts of speech in almost any order. Just keep the grammatical cases as they are, keep the finite part of the verb at position 2 and the infinite part at the end. You will get a lot of different sentences, that all translate into the same English sentence, but this doesn't mean, that they mean exactly the same. The differences in meaning are very subtile, and English has no grammatical tools to express those subtile differences:
- Mein Vater hat unserem Nachbarn den alten Rasenmäher geliehen.
- Mein Vater hat den alten Rasenmäher unserem Nachbarn geliehen.
- Unserem Nachbarn hat mein Vater den alten Rasenmäher geliehen.
- Den alten Rasenmäher hat mein Vater unserem Nachbarn geliehen.
The subject can not stand behind the dative or accusative object, but it is difficult to explain why. (I described it in another answer.)
All four sentences translate into:
My father lent our old lawn mower to our neighbor.
The subtiles differences in meaning only change the focus, i.e. it sets the syntactical highlight to different parts of speech. Number 1 ist the standard version. In all other versions you highlight those parts of speech, that do not stand on the same position as in #1. The highlight effect becomes stronger on position 1. So in #3 you set the focus on the fact, that something was lent to our neighbor, while in #4 you lead the attention to the fact, that it was the old loan mover that was lent.
But in four sentences you say the same:
- My Father did something
Subject in nominative case in German
Position 1 in English
- the action, that was done, was lending something
Position 2 in both languages
- our old loan mover is the thing that was lent.
Accusative case in German
Direct object in English, has to stand close to the verb (which means: fixed position)
- to out neighbor is the receiver of the loan mower
Dative case in German
Indirect Object in English, doesn't need to be placed near to the verb (which in this specific sentence again means: fixed position)
Er hilft der Frau beim Überqueren der Straße.
He helps the Lady to cross the street.
Literally (but bad English): He helps the lady at the crossing of the street.
(The correct German translation of »He helps the Lady to cross the street.« is: »Er hilft der Frau die Straße zu überqueren.« So when you translate the original German sentence into good English, and then translate it back into German you get a sentence, that is different from the original sentence, because in German you have more possibilities to express this specific fact.)
Wer? → nominative case (and because there is no other part of speech in nominative case in this sentence, this must be the subject)
Verb at position 2
- der Frau
Wem? → dative case (who receives the help?)
beim Überqueren der Straße
This part of speech begins with a preposition, so it is a prepositional object. It doesn't stand in any of the four cases. But you can split it up in smaller parts (note: beim = bei dem):
- bei (part of beim)
- dem Überqueren (the article dem is the other part of beim)
- der Straße
But remember, that »beim Überqueren der Straße« still is one part of speech. If you move it, you only can move it as one block. You can't split it up without changing the meaning of the sentence
You can rearrange those parts of speech, and will get these correct German sentences, that all will result in the same english translation:
- Er hilft der Frau beim Überqueren der Straße.
- Der Frau hilft er beim Überqueren der Straße.
- Beim Überqueren der Straße hilft er der Frau.
All other word orders you might think of are invalid, due to rules not discussed here (see above).
What google gave you is wrong. Here are the correct translations of googles sentence:
The woman helps him cross the street.
- Die Frau hilft ihm beim Überqueren der Straße.*
- Ihm hilft die Frau beim Überqueren der Straße.
- Beim Überqueren der Straße hilft ihm die Frau.
- Beim Überqueren der Straße hilft die Frau ihm.
* More correct would be: »Die Frau hilft ihm, die Straße zu überqueren« but I want to stay consistent with the examples above.
Learn the differences:
- die Frau = nominative case (and therefore the subject)
- der Frau = dative case (and therefore can't be the subject)
- er = nominative case (and therefore the subject)
- ihm = dative case (and therefore can't be the subject)