I seem to get these two words constantly mixed up in speaking. Is someone able to help me out by providing some examples that will help me remember the difference? I tend to just guess normally.
"Machst du noch lange?" - Would that mean "Are you working late?"
As for "länger" I can't even think of a specific example I use, but I'm finding I throw it incorrectly into sentences here and there as it's something I've heard said by others.
While länger is the comparative from of lang, in your example no comparison takes place. One could claim, that als ein paar Minuten (than a few minutes) was meant, but omitted, however.
But it is useful to know, that there is a construction called absoluter Komparativ (English: unbalanced comparative), e. g.
Ich führte ein längeres Gespräch (I had a lengthy talk)
where comparatives are used in a non-standard form: You don't want to so be rude to state alter Mann (old man), but use älterer Mann (elder man). This is unexpected, since the comparative actually means a weaker form than the positive alt
Don't worry too long or any longer, these two can often make the same sense pragmatically, in my opinion. But I think there can be a difference if the language is used carefully.
Länger is the comparing form, but the object of the comparison is not explicit in the familiar use you seem to refer to, just context.
If I am already decided to leave the party, I might ask you if you will stay longer, bleibst du noch länger, while i am leaving. Länger means longer than I do in that situation.
Before that decision, I might have asked you "bleibst du noch lange", to know if it makes sense for me to wait for you, so that we can share rides.
But often both forms are used in both situations. Simply because länger can also mean longer than until just now.
Länger = Lang + er means just longer, as in the following:
(...) nicht länger du musst arbeiten als normal(...)
Which means:
(...) you musn't work more than normal (or longer than normal)(...)
In colloquial language "länger" can also mean "quite a time". e.g. "Ich habe sie länger nicht gesehen" - "I haven't seen her for quite a time" compared to "Ich habe sie lange nicht gesehen" - "I haven't seen her for a long time". "Länger" in this sentence actually means a shorter period than "lange".
Adjectives modify a noun or noun phrase, adverbs modify a verb or verb phrase.
länger adj. (comparative of lang) "longer"
The adjective lang denotes a length of an object or timespan:
- Der Fluss ist 100 km lang. "The river is 100 km long."
- Die Ferien sind nicht lang genug. "The holidays aren't long enough."
The comparative compares the lengths of two objects or timespans:
- Dieser Fluss ist länger als der andere. "This river is longer than the other."
- Meine Ferien sind länger als deine. "My holidays are longer than yours."
lange adv. "long"
The adverb lang means that some event is lasting for a certain time:
- Heute schläft er lange. "Today he is sleeping long."*
- Er bleibt lange weg. "He is staying out long."*
* In English you would probably not use long but use other words to express these thoughts, e.g. today he is sleeping in or he is staying out late.
What might be confusing is that lang is the colloquial form of the adverb lange, and that lange is also one of the inflected forms of the adjective lang:
Die lange Straße und der lange Abend sind beide lang. "Both the long street and the long evening are long."
Er bleibt lang(e) weg. "He stays out late (lit. long)."
What you might want to do is learn about adjectives and adverbs.
