Šivanje mi pomaže poslije napornog dana.

It is a noun.

More specifically, šivanje is a verbal noun formed from a verb meaning to sew. In this sentence it means sewing as an activity, just like English sewing in Sewing helps me.

So grammatically:

• šivanje = the activity of sewing
• it behaves like a singular noun
• it is neuter

That is why it can be the subject of the sentence.

Mi is the dative singular form of ja (I).

Here it means to me, but in natural English we usually translate it simply as me:

• Šivanje mi pomaže = Sewing helps me

This is because the verb pomagati (to help) normally takes the person being helped in the dative in Croatian.

So:

• mi = to me
• ti = to you
• mu / joj = to him / to her

A learner often expects the equivalent of English direct object me, but Croatian uses the dative with this verb.

Because the subject is šivanje, which is third person singular.

The verb has to agree with the subject:

• šivanje = singular
• therefore pomaže = helps

It is not agreeing with mi.
Mi is just the person receiving the help.

So the structure is:

• šivanje = subject
• mi = indirect object / dative recipient
• pomaže = verb agreeing with šivanje

Because poslije requires the genitive case.

The base form would be:

• naporan dan = a tiring/hard day

After poslije (after), both words change to genitive singular:

• napornog dana = after a tiring day

So:

• naporan → napornog
• dan → dana

This is normal case agreement: the adjective changes to match the noun.

When poslije is used as a preposition before a noun, yes, it normally takes the genitive:

• poslije ručka = after lunch
• poslije škole = after school
• poslije napornog dana = after a tiring day

You may also see nakon, which also means after and also takes the genitive:

• nakon napornog dana

Both are correct; poslije is very common in everyday speech.

The order is natural because mi is a clitic. Croatian clitics usually appear near the beginning of the sentence, often after the first stressed word or phrase.

So:

• Šivanje mi pomaže = natural, neutral

You can move things around in Croatian more than in English, but the meaning or emphasis may change. For example:

• Meni šivanje pomaže = Sewing helps me with extra emphasis on me
• Šivanje pomaže meni = also possible, but meni is stressed and sounds emphatic

For a neutral sentence, Šivanje mi pomaže is the best pattern.

Both can mean to me, but they are used differently.

• mi = short, unstressed clitic form
• meni = full, stressed form

In a normal neutral sentence, Croatian usually prefers the clitic:

• Šivanje mi pomaže = neutral

Use meni when you want emphasis or contrast:

• Meni šivanje pomaže, ali njemu ne.
  Sewing helps me, but not him.

So in your sentence, mi is the natural choice.

Yes, very close.

English sewing can function as a verb form or a noun-like form. In Croatian, šivanje is clearly a noun naming the activity.

So in this sentence, it works much like an English gerund:

• Sewing helps me
• Šivanje mi pomaže

Other similar Croatian verbal nouns are:

• čitanje = reading
• pisanje = writing
• učenje = studying / learning

This is about aspect.

• pomagati = imperfective
• pomoći = perfective

Pomaže comes from pomagati, and it fits a general, repeated, or ongoing idea:

• Šivanje mi pomaže poslije napornog dana.
• Sewing helps me after a tiring day.

This means it is generally true, not just one single completed event.

A perfective form would usually suggest a single completed act or a future/conditional meaning, depending on context. So pomaže is the right choice here.

Yes, Croatian present tense can sometimes correspond to either:

• helps
• is helping

Context decides.

In this sentence, the most natural interpretation is a general truth or habit:

• Sewing helps me after a tiring day

But grammatically, Croatian present tense is less rigid than English about this distinction.

Yes, but the meaning changes.

• Šivanje mi pomaže = Sewing helps me
• Šivanje pomaže = Sewing helps / Sewing is helpful

If you remove mi, the sentence becomes more general and no longer says who is being helped.

So mi is important if you want the personal meaning helps me.