wǒ xiàbān yǐhòu bù xiǎng chūmén.

下班 literally means “to get off work / to finish one’s shift.”

• 上班 (shàngbān) = to go to work / to be on duty
• 下班 (xiàbān) = to get off work / to finish work for the day

So 我下班以后不想出门 is better understood as:
“After I get off work, I don’t want to go out.”
not just “After work (in general) I don’t want to go out.”

以后 means “after / later” and marks a time after something.

• 我下班以后不想出门。
  “I don’t want to go out after I get off work.”

If you say 我下班不想出门, it sounds incomplete or odd, because 下班 usually needs something like 以后 or 了 to make the “after finishing work” time clearer.

You can say:

• 下了班以后，我不想出门。 (very natural)
• 下班以后，我不想出门。 (also natural)

Leaving 以后 out usually requires 了:

• 下了班，我就不想出门。
  “Once I’m off work, I don’t want to go out.”

Yes. Time expressions are very flexible in Chinese. Both are natural:

• 我下班以后不想出门。
• 下班以后，我不想出门。

Putting 下班以后 at the beginning is slightly more “topic-comment” and sounds very natural in spoken Chinese:
“As for after work, I don’t want to go out.”

Both can relate to “not wanting”, but the nuance is different:

• 不想出门 = “don’t feel like going out / don’t want to go out (inwardly, by preference)”
  
  • softer, about inner desire / inclination
• 不要出门 = “don’t go out / don’t you go out”
  
  • often sounds like a command / instruction / warning

In your sentence, we’re talking about how I feel, so 不想出门 is the natural choice.
不要出门 would sound like telling someone else “Don’t go out.”

In this sentence, 想 means “to want / to feel like (doing something)”.

Common meanings of 想:

1. want to / feel like
   
   • 我想吃饭。 = I want to eat.
2. think / consider
   
   • 我想，这样不太好。 = I think this isn’t very good.
3. miss (someone)
   
   • 我很想你。 = I miss you a lot.

Context tells you the meaning. With a verb right after (想出门), it usually means “want to / feel like (doing X)”.

They’re related but not exactly the same:

• 出门 = to go out (of the house / door / indoors), often implying “go out in general”
  
  • 我不想出门。 = I don’t want to go out (leave home / go outside).
• 出去 = “go out” in a more directional sense (outwards from here).
  
  • 我要出去一下。 = I’m going out for a bit.

In your sentence, 出门 is perfect: it expresses the general idea of leaving home / going out without specifying the direction too precisely.

Yes, you can say 不想出去, and it’s also natural. Nuance:

• 不想出门 – emphasizes leaving the door/home/indoors; very common in everyday speech.
• 不想出去 – emphasizes the direction “out(wards)” from where you are.

In practice, in this context, both usually mean basically the same:
“I don’t feel like going out after work.”

Yes, in a suitable context you can omit 我, and people will understand it refers to you:

• (我) 下班以后不想出门。

Chinese often drops the subject when it’s obvious from context.
But in isolation (like in a textbook example), including 我 is clearer.

Chinese doesn’t use verb changes (like work / worked) for tense.
Time is usually expressed with time words and context, here:

• 下班以后 = after (I) get off work

Depending on context, the sentence could mean:

• general habit:
  
  • “After work, I (generally) don’t want to go out.”
• about today / future:
  
  • “After I get off work (today), I don’t want to go out.”

If you need to be specific, you add time words:

• 今天下班以后，我不想出门。
  After work today, I don’t want to go out.
• 以后下班以后，我都不想出门。
  In the future, after work I never feel like going out.

Both are grammatical and common:

• 我下班以后不想出门。
• 我下了班以后不想出门。

Nuance:

• 下班以后 – a bit more neutral and slightly more “timeless” / general.
• 下了班以后 – 了 can make the action feel more clearly completed, often fitting concrete situations (today, a specific time), e.g.:
  
  • “After I’ve finished work, I don’t want to go out.”

In everyday speech, people use both; the difference is subtle.

Putting 以后 right after 我 changes the meaning:

• 我下班以后不想出门。
  = After I get off work, I don’t want to go out.

• 我以后下班不想出门。
  Literally: “I in the future, when I get off work, don’t want to go out.”
  This sounds awkward and unclear; it seems to say “from now on, whenever I get off work, I don’t want to go out”, but native speakers would phrase that differently:

  • 以后我下班就不想出门了。
  • 以后下班我都不想出门。

So for the simple “after work, I don’t want to go out,” keep 以后 after 下班:
下班以后.

In isolation, 不 is bù (4th tone), but there is a tone sandhi rule:

• 不 changes to bú (2nd tone) when followed by a 4th-tone syllable.

想 (xiǎng) is 3rd tone, so 不 stays bù:

• 不想 (bù xiǎng)

Examples of the change:

• 不对 → bú duì
• 不是 → bú shì

So in your sentence it’s: wǒ xiàbān yǐhòu bù xiǎng chūmén.