Mein Freund hofft trotzdem, dass der Vertrag später unbefristet wird.

Trotzdem means nevertheless, all the same, or still.

It signals a contrast with something mentioned earlier. In other words, there is some reason to doubt or be pessimistic, but he hopes anyway.

So the feeling is not just simple hope, but hope despite something.

Because dass introduces a subordinate clause, and in German, subordinate clauses are normally separated from the main clause with a comma.

So the structure is:

• main clause: Mein Freund hofft trotzdem
• subordinate clause: dass der Vertrag später unbefristet wird

This comma is required in standard German.

No. They are different words.

• dass = that as a conjunction
  
  • Ich weiß, dass...
• das = the, that, or which, depending on context
  
  • das Haus
  • Das ist gut.

A useful shortcut:

• If it introduces a whole clause, it is usually dass
• If it replaces or accompanies a noun, it is usually das

In your sentence, dass is a conjunction introducing the clause der Vertrag später unbefristet wird.

Because after dass, German uses subordinate clause word order, and the conjugated verb goes to the end.

Compare:

• Main clause: Der Vertrag wird später unbefristet.
• Subordinate clause: ..., dass der Vertrag später unbefristet wird.

This is one of the most important German word-order rules:

• main clause: conjugated verb in second position
• subordinate clause: conjugated verb goes to the end

Because the subject is der Vertrag, which is third person singular.

The verb werden is conjugated like this:

• ich werde
• du wirst
• er/sie/es wird
• wir werden
• ihr werdet
• sie/Sie werden

Since der Vertrag = it, the correct form is wird.

Because German very often uses the present tense to talk about the future, especially when there is a time word like später.

So wird here is grammatically present tense, but the meaning is future because später makes the time clear.

This is completely normal German. English does something similar sometimes too:

• Tomorrow I leave early.

German does this even more freely.

Here werden means to become.

So:

• unbefristet sein = to be permanent / open-ended
• unbefristet werden = to become permanent / open-ended

That is why werden is the right verb here: the contract is not yet permanent, but your friend hopes it later becomes permanent.

If you used ist instead, the meaning would change:

• ..., dass der Vertrag unbefristet ist
  = the contract already is permanent

But the sentence is about a hoped-for future change, so wird fits best.

Because it is not directly in front of a noun here. It is used predicatively after werden.

Compare:

• ein unbefristeter Vertrag
  Here the adjective is attributive and comes before the noun, so it takes an ending: -er
• Der Vertrag wird unbefristet
  Here the adjective is predicative, so it takes no ending

This is the same pattern as:

• ein guter Mann
• Der Mann ist gut

So unbefristet has no ending because it is linked to der Vertrag through wird.

Der Vertrag is in the nominative case because it is the subject of the subordinate clause.

Ask yourself: What becomes unbefristet?
Answer: der Vertrag

That makes it the subject, so nominative is correct.

Also, Vertrag is a masculine noun, so in nominative singular it is der Vertrag.

Because mein is being used as a possessive determiner directly before the noun Freund.

For a masculine noun in the nominative singular, the correct form is:

• mein Freund

This works like:

• mein Bruder
• mein Vater

Meiner usually appears when the possessive word stands without a noun, or in other grammatical roles. For example:

• Das ist meiner. = That one is mine.

But before Freund, you need mein, not meiner.

Später means later and gives the time reference for wird unbefristet.

It tells you when the contract is hoped to become permanent.

So the idea is not just that the contract becomes permanent, but that it happens at a later point, not now.

Yes. German main clauses follow the verb-second rule, so different elements can come first.

Your sentence starts with the subject:

• Mein Freund hofft trotzdem, dass ...

But you could also front trotzdem:

• Trotzdem hofft mein Freund, dass ...

Both are grammatical. The difference is mainly focus:

• Mein Freund first = focus starts on my friend
• Trotzdem first = stronger emphasis on the contrast, nevertheless

The verb still stays in second position in the main clause:

• hofft

So when trotzdem moves to the front, the subject moves after the verb.

Sometimes yes, but its position affects emphasis.

The version here:

• ..., dass der Vertrag später unbefristet wird

is a very natural, neutral order.

You may also hear other arrangements in some contexts, but they can sound more marked or emphasize a different part of the sentence. For a learner, the version in your sentence is a very good standard model.

So the safest takeaway is:

• dass + subject + time word + predicate + verb at the end

which is exactly what you have here.