Hon jämförde två kontrakt länge innan hon bestämde sig för vilket jobb hon ville ha.

Because jobb is a neuter noun in Swedish. Its basic form is ett jobb, so when you use which, you need the neuter form vilket.

• en-word → vilken
• ett-word → vilket
• plural → vilka

So:

• vilken bil = which car
• vilket jobb = which job
• vilka kontrakt = which contracts

Since jobb is an ett-word, vilket jobb is correct.

Bestämde sig för is a very common Swedish expression meaning decided on or made up her mind about.

It comes from the verb bestämma sig för, which is reflexive:

• Jag bestämmer mig för något = I decide on something
• Hon bestämde sig för något = She decided on something

Here is what each part does:

• bestämde = past tense of bestämma
• sig = reflexive pronoun, here meaning something like herself
• för = the preposition required by this expression

So you should learn bestämma sig för as one whole unit.

Compare:

• Hon bestämde sig för jobbet = She decided on the job
• Hon bestämde sig för att flytta = She decided to move

Because ville ha means wanted to have / wanted to get, and in this sentence that is the natural way to express choosing a job.

• ville = wanted
• ha = have

So vilket jobb hon ville ha literally means which job she wanted to have.

In English, we often just say which job she wanted, but Swedish often uses ha in this kind of context.

Compare:

• Jag vill ha kaffe = I want coffee
• Hon ville ha jobbet = She wanted the job
• Vilket jobb hon ville ha = Which job she wanted

Using just ville without ha would usually need some other complement and often would not sound as natural here.

Because this is an embedded question inside a larger sentence, not a direct question.

Direct question:

• Vilket jobb ville hon ha? = Which job did she want?

Embedded question:

• ... vilket jobb hon ville ha = ... which job she wanted

In Swedish, embedded questions usually keep subject + verb order:

• Jag vet inte var han bor = I do not know where he lives
• Hon frågade vilken bok jag läste = She asked which book I was reading
• ... vilket jobb hon ville ha = ... which job she wanted

So there is no inversion here.

Because innan hon bestämde sig för vilket jobb hon ville ha is a subordinate clause.

In Swedish, subordinate clauses normally have regular subject + verb order:

• innan hon bestämde sig
• eftersom han var trött
• när vi kom hem

Inversion is common in main clauses, especially when something comes first:

• Sedan bestämde hon sig = Then she decided
• I går kom han hem = Yesterday he came home

But after subordinating words like innan, att, eftersom, när, om, you normally do not invert.

Innan means before.

In this sentence it introduces the time clause:

• Hon jämförde två kontrakt länge innan ...
• She compared two contracts for a long time before ...

Swedish innan can be followed by:

1. A clause

   • innan hon bestämde sig = before she decided

2. A noun phrase

   • innan mötet = before the meeting

It is a very common word for sequencing events in time.

Länge means for a long time or for long.

Here it tells us how long she compared the contracts:

• Hon jämförde två kontrakt länge = She compared two contracts for a long time

It is an adverb of duration.

A few useful comparisons:

• länge = for a long time
• lång = long
• långt = far / a long way, or sometimes long as an adverb in other contexts

Examples:

• Vi väntade länge = We waited a long time
• Det tog lång tid = It took a long time

So in your sentence, länge modifies jämförde.

Because the plural of kontrakt is also kontrakt.

This is a neuter noun with the same form in singular indefinite and plural indefinite:

• ett kontrakt = a contract
• två kontrakt = two contracts

The definite forms are:

• kontraktet = the contract
• kontrakten = the contracts

So this pattern is completely normal:

• ett jobb, två jobb
• ett kontrakt, två kontrakt

Because Swedish normally requires an explicit subject in each clause.

So you get:

• Hon jämförde ...
• innan hon bestämde sig ...

Even though it is the same person, Swedish still says hon again in the subordinate clause.

This is the same idea as in English:

• She compared two contracts for a long time before she decided ...

You also repeat hon again inside the embedded clause:

• ... vilket jobb hon ville ha

That is normal and necessary.

Yes. The infinitive is jämföra, meaning to compare, and jämförde is the past tense:

• att jämföra = to compare
• jämför = compare / compares
• jämförde = compared
• har jämfört = have/has compared

So:

• Hon jämför två kontrakt = She compares two contracts
• Hon jämförde två kontrakt = She compared two contracts

Yes, but the tone would change a bit.

• jobb = the most everyday, common word for job
• arbete = work / job, sometimes a bit broader or slightly more formal depending on context
• tjänst = post, position, appointment; more formal, often used in professional or official contexts

So vilket jobb hon ville ha sounds natural and conversational.

Possible alternatives:

• vilket arbete hon ville ha = possible, but less casual
• vilken tjänst hon ville ha = more formal, more like which position

So jobb is probably the most natural choice in ordinary speech.