How to know which form of "all, alle, allen, aller, allem, alles" to use?

Question

I've mainly just used alle or alles up until now to represent all or every.

However there are multiple declinations for "all" that are quite confusing (including aller, allen, allem). But then in other examples, one can also just simply use all.

For example:

ALLE Hunde essen Fleisch

ALL meine Freunde lesen Bücher

Er kann ein Haus kaufen mit ALL seinem Geld

Ich habe ALLEN bescheid gesagt, dass...

ALL die schönen Blumen.

My subsequent questions are as follows:

1) Why is "all" used here in ALL meine Freunde lesen Bücher and Er kann ein Haus kaufen mit ALL seinem Geld and not "alle"?

2) Why has it changed to "Ich habe ALLEN bescheid gesagt, dass..."?

3) When then with examples if possible, does one simply use alles?

and 4) why is it:

alle meine besten Freunde

but

all der Wein. (both sentences seem to say "all of the etwas..")

Answer 1

All is an indefinite pronoun with adjective declination.

The indefinitum all can connect with following pronouns. The personal ending of all is then shown in the following pronoun only:

All meine Freunde.

If no other pronoun follows all, the normal personal ending is suffixed:

Alle Freunde.

Answer 2

Concerning your 3rd question, "alles" is mostly used to describe non-specific objects. Ich habe alles verloren. (I have lost everything), but Ich habe alle Bücher verloren. (I have lost all my books).

The difference between alle meine Freunde and all der Wein is, as Jublo mentioned, declination. Meine Freunde is plural, hence alle (die Freunde), but der Wein is singular, hence all der Wein.

Answer 3

You should have a good grammar for German to get an overview of the special adjectve "all" . The German adjective declensions are complicated enough and function adjectives such as "all/alle" have peculiarities. Without the help of a grammar you won't get far in this complicated area.

As to your question "all die schönen Blumen" - here the plural form "alle" is simply reduced to "all" - a simple shortening. "Die schönen Blumen" clearly indicates plural. So it is not absolutely necessary to indicate plural a second time by using "alle". You can drop the -e because of redundancy and to make the noun group with "Blumen" shorter. This noun group is relatively long with three sub-elements before "Blumen" so it is natural to shorten "alle" to "all".