Am Ende des Tages sind meine Hände schmutzig, aber ich bin zufrieden, weil der Garten viel schöner aussieht.

It literally means at the end of the day.

In this sentence, it most naturally sounds literal: after a day of gardening, the speaker’s hands are dirty.

But German also uses am Ende des Tages idiomatically, just like English, to mean something like when everything is taken into account. So it can be either literal or figurative depending on context.

Because Ende often takes the genitive:

• das Ende des Tages = the end of the day

Then an dem Ende des Tages becomes am Ende des Tages.

So the structure is:

• an dem → am
• Ende
  • genitive
• des Tages

This is a very common fixed expression.

Because German main clauses follow the verb-second rule.

That means the finite verb must come in the second position of the clause. If you put a time expression first, the verb still has to stay second:

• Am Ende des Tages = first position
• sind = second position
• meine Hände = comes after the verb

So:

• Am Ende des Tages sind meine Hände schmutzig.

This does not mean the subject has disappeared or changed. It is still meine Hände.

Hände is the plural of Hand.

Here it is the subject of the clause, so it is in the nominative plural:

• meine Hand = my hand
• meine Hände = my hands

And because the subject is plural, the verb is plural too:

• meine Hände sind = my hands are

Because it is a predicate adjective, not an adjective directly in front of a noun.

Compare:

• schmutzige Hände = dirty hands
  
  • adjective before the noun → needs an ending
• Die Hände sind schmutzig = The hands are dirty
  
  • adjective after sein → no ending

The same idea applies to zufrieden later in the sentence:

• ich bin zufrieden

For two different reasons:

• aber joins two main clauses, and German normally separates them with a comma:
  • ..., aber ich bin zufrieden
• weil introduces a subordinate clause, and subordinate clauses are separated by a comma:
  • ..., weil der Garten viel schöner aussieht

So both commas are standard and expected here.

Because weil introduces a subordinate clause, and in German subordinate clauses the finite verb usually goes to the end.

Main clause:

• Der Garten sieht viel schöner aus.

Subordinate clause:

• ..., weil der Garten viel schöner aussieht.

So the word order changes because of weil.

aussehen is a separable verb meaning to look / to appear.

In a main clause, it splits:

• Der Garten sieht viel schöner aus.

In a subordinate clause, it stays together and goes to the end:

• ..., weil der Garten viel schöner aussieht.

So this sentence is a good example of how separable verbs behave differently depending on clause type.

schöner is the comparative form of schön:

• schön = beautiful / nice
• schöner = more beautiful / nicer

viel schöner means much nicer or a lot more beautiful.

With comparatives, German often uses:

• viel = much / far
• etwas = somewhat
• ein bisschen = a little

So:

• viel schöner = much nicer

sehr schöner is not the normal way to form this idea. If you want a comparison, use the comparative:

• schöner
• viel schöner

Because der Garten is the subject of aussieht.

The garden is the thing that looks nicer:

• der Garten sieht ... aus

So it must be in the nominative:

• der Garten

If it were a direct object, you might expect den Garten, but that is not what is happening here.

Yes, often you can, but the grammar changes.

With weil, the verb goes to the end:

• ..., weil der Garten viel schöner aussieht.

With denn, the following clause keeps normal main-clause word order:

• ..., denn der Garten sieht viel schöner aus.

So both can mean because, but:

• weil = subordinate clause, verb at the end
• denn = coordinating conjunction, normal word order

Yes, ich bin zufrieden is very common.

It means:

• I am satisfied
• I am content
• sometimes I’m happy with the result

In this sentence, it means the speaker feels good about the gardening work, even though their hands are dirty.

No. German is flexible, as long as you keep the verb-second rule in main clauses.

For example, you could also say:

• Meine Hände sind am Ende des Tages schmutzig, aber ich bin zufrieden, weil der Garten viel schöner aussieht.

That version puts more emphasis on meine Hände first.

The original sentence sounds very natural because it sets the time frame right away:

• Am Ende des Tages ...