Замість того щоб сперечатися, ми заповнимо заяву на повернення.

It is a set expression meaning instead of doing ....

Structure:

• замість = instead of
• того = literally that, but here it is part of the fixed pattern
• щоб = so that / in order to / that

Together, замість того щоб + infinitive means instead of + -ing in English.

So:

• Замість того щоб сперечатися = Instead of arguing

A useful comparison:

• замість кави = instead of coffee
• замість того щоб пити каву = instead of drinking coffee

So when Ukrainian wants to say instead of doing something, this full pattern is very common.

Because замість того щоб is being treated as one unit, a compound conjunction.

In this sentence:

• Замість того щоб сперечатися = subordinate clause
• ми заповнимо заяву на повернення = main clause

Since the subordinate part comes first, Ukrainian puts a comma before the main clause:

• Замість того щоб сперечатися, ми заповнимо...

So the comma marks the boundary between the two parts of the sentence, not a break inside замість того щоб.

Because after замість того щоб, Ukrainian normally uses an infinitive to express the action being replaced.

So:

• замість того щоб сперечатися = instead of arguing
• замість того щоб чекати = instead of waiting
• замість того щоб телефонувати = instead of calling

This is very natural in Ukrainian. English often uses an -ing form, but Ukrainian uses the infinitive here.

The -ся is a reflexive/middle marker that is part of the verb.

The dictionary form is:

• сперечатися = to argue, to dispute

In many Ukrainian verbs, -ся does not always translate as a separate word like oneself. Often it is just part of the normal verb.

So you should learn:

• сперечати — not the normal verb here
• сперечатися — the standard verb meaning to argue

Other similar verbs:

• сміятися = to laugh
• боятися = to be afraid
• здаватися = to seem

Заповнимо is first person plural future: we will fill out / we will complete.

It comes from the perfective verb:

• заповнити = to fill out, complete

Perfective Ukrainian verbs use forms that look like present tense, but their meaning is future:

• я заповню = I will fill out
• ми заповнимо = we will fill out

So in this sentence:

• ми заповнимо заяву = we will fill out the form

If you wanted an imperfective idea, you would use something like:

• ми будемо заповнювати = we will be filling out

But here the perfective fits well because the action is seen as a complete result.

Because заяву is the accusative singular form, used for the direct object of the verb.

Base form:

• заява = application, statement, request, form

After заповнити / заповнимо (to fill out), the thing being filled out is the direct object, so it goes in the accusative:

• заповнити заяву = to fill out an application/form

For feminine nouns ending in -а, the accusative singular often changes to -у:

• книга → книгу
• форма → форму
• заява → заяву

It means something like a return request, a return form, or an application for a refund/return, depending on context.

Breakdown:

• заява = application, request, statement
• на = for
• повернення = return / giving back / refund

So:

• заява на повернення = a request/form for a return

This is a common pattern in Ukrainian:

• заява на отримання візи = an application for receiving a visa
• заява на відпустку = a leave request
• заява на обмін товару = a request to exchange a product

Because after заява на ..., Ukrainian normally uses a noun, not an infinitive.

Here:

• повернення is a verbal noun meaning return or returning

So Ukrainian says:

• заява на повернення = request/form for return

Not:

• заява на повернути ❌

This is very similar to English preferring a noun in phrases like:

• application for refund
• request for return

rather than application for to return.

It is accusative singular, because на here means for and governs the accusative.

The noun повернення is neuter and inanimate, and for this type of noun the accusative looks the same as the nominative:

• nominative: повернення
• accusative: повернення

So the form does not change, even though the case does.

Usually, with a verb idea like instead of arguing, the normal expression is замість того щоб + infinitive.

So:

• Замість того щоб сперечатися... = natural

If you remove того, the phrase sounds incomplete or unnatural in standard usage:

• Замість щоб сперечатися... = much less standard / not what learners should aim for

So as a learner, it is best to remember the full pattern:

• замість того щоб + infinitive

Yes, somewhat. Ukrainian word order is more flexible than English, but the original order is very natural.

Original:

• Замість того щоб сперечатися, ми заповнимо заяву на повернення.

You could also say:

• Ми заповнимо заяву на повернення замість того щоб сперечатися.

Both are grammatical, but the first version emphasizes the contrast right away:

• Instead of arguing, ...

That makes it sound especially natural in advice, decisions, or problem-solving situations.