[Noob] Different "Receive" Amounts in ledgers

I just spend my first €50 on crypto and am already wondering about future taxes. I saw there is a discrepancy in the amounts received in the different fields.

In the image above amounts for Uniswap and Bitcoin Cash can be attributed to rounding errors, but Bitcoin shows both as 0.00012 BTC and 0.00013 BTC . That's a difference of about 8% !

Also, nowhere does it say the exchange rate. There is no receipt on the site, or PDF per E-Mail (as proof for taxation). I already requested the CVS-Exports. The amounts I received into my Kraken account are those on the left, but the transaction details say numbers that are bigger.

Thus in an event of taxation I will be taxed by what I can prove, even though what I received is less.

I also saw that even though I have spent €5 on each coin, for whatever reason the Fee for BTC was 1 cent less, and the amount 1 cent more, than any other coin. Is the fee for BTC different?

Where can I get proper documentation for the coins I bought? Do I make screenshots with every trade? I have read here https://support.kraken.com/hc/en-us/articles/360001184966-Kraken-does-not-provide-tax-forms-or-statements :

If you require a record of your balance or trade history, click here for instructions on how to export your data to a CSV-file.

We are currently unable to provide account history in pdf format.

So is the CVS-file the only proof that I purchased/sold anything? There is no receipt?

I apologize for nooby questions, am happy to be on board =)

Edit: my export just finished processing, the CVS file says I received
0.0049900000 BCH (rounding error)
0.1601500000 UNI (rounding error)
0.0001251400 BTC (again a completely different value)

I am not sure why the rounding errors are here. There are enough decimal points shown. The value for BTC is just completely different.