1) We paid more for the repairment of the old phone up to now thanthan buying a new one.

Repairment isn’t really used or it isn’t a word. The use of “new phone means that it would be better to add in “old” as well.
“A new one” in my correction could also be changed to “the new one” depending on the situation.

2) He submitted his quotation according toto get as much VAT refund as possible.

“According to” is used when referencing a different source (for example a website or another person).

3) What do you expect youto find in my notebooks.

If you really wanted to still use “you” it would sound better as something like “what do you expect for you to find in my notebooks?” But that sounds very stiff and unnatural.

4) Could you please explain me thewhich attached receipts belong to whatich invoices?

I had to search this up to be entirely sure of the explanation but:
“What” would be used if there’s a more or less infinite amount of possible answers (as in an unrestricted number of answers)
Whereas “which” is used when the answer should be something that you’ve already listed (a restricted number of possible answers). Think “which of these…”

Because there is no specific explanation in the bank receipts. ¶
ANOTHER OPTION: I’m unsure because there is no specific explanation in the bank receipts.

This is right but because typically sounds better in the middle of a sentence (or in casual situations this works). When because is used at the beginning of a sentence (in formal cases at least) it would typically be “because of this” or something like that. But this wouldn’t make sense here because “because of this” suggests that the previous statement causes the next one, but “because” in this case is clarifying that the previous statement happened as a result of the next one.

“Clear” might sound better instead of “specific”.

This is not enough for the VAT refund process.

But I’m also not entirely sure what this means.

We will submit these receipts to the tax office as evidence thato shows that the payment was brought to Azerbaijan.

1) We paid more for repairment ofing the phone up toil now than new one.

2) He submitted his quotation according tofor as much VAT refund as possible.

3) What do you expect youto find in my notebooks.

or "you will find"

4) Could you please explain meto me which invoices the attached receipts belong to what invoices?

This is not enough for the VAT refund process.

We will submit these receipts to tax office as evidence thato shows that the payment was broughsent to Azerbaijan.

BETTER: Some Random Sentences

1) We have paid more forto repairment of the phone up to now than the old phone than the price of a new one. ALSO POSSIBLE: We have wasted money repairing the old phone: it would have cheaper to buy a new one.

2) He submitted his (price) quotation according to as much VAT refund as possibleto maximize his VAT refund.

PUNCTUATION: Add a question mark at the end - 3) What do you expect you find in my notebooks.?

4) Could you please explain me theto me which attached receipts belong to whatgo with which invoices?

Because there is no specific explanation inCLEARER: It is unclear which invoice which invoices the bank receipts belong to.

The explanation on the receipt isIN AMERICAN ENGLISH: The receipt claims to be a “bank transfer from BCCs Italy”.”

PUNCTUATION: In American English, final periods (.) *ALWAYS* come _before_ end quotes ("). Sometimes this is not so in British English, but is always so in American English.

MY GUESS: This is not enough for VAT refund processmoney to merit a VAT refund. ALSO POSSIBLE: Not enough money was spent to warrant a VAT refund.

We will submit these receipts tothe tax office as evidence thato shows the payment was brought to Azerbaijan.