I found one website but there it types - it doesn't matter how many BTC you send you will get same fee. And there types that now fee for a transaction is 0.6$. It is really so low ? I don't really trust the fee can be so low
Is there a website where I can write amount of BTC I want to send and it check the fee in real time?
Bitcoin transaction fees are based on transaction size, not amount. We measure fees in "satoshis per byte" -- a satoshi = 0.00000001 BTC. Users compete for block space -- higher fee transactions get confirmed faster than low fee transactions.
This is the tool I use to check network fees. It shows how many transactions are waiting to be confirmed at various fee rates. Right now, 2-3 satoshis/byte will probably get confirmed in the next block. Earlier in the day, you needed closer to 7 satoshis/byte for the same confirmation speed.
How I can know how many bytes my transaction have? It's just send btc from one wallet to another
Any good wallet will allow you to manually set the fee rate without worrying about the size. For beginners, I suggest Electrum. It has a slider that allows you to choose based on how urgent your transaction is. For increased precision, I manually enter the fee -- I prefer to pay very low fees and wait for confirmation -- and then I click "Preview transaction" to confirm it has the correct satoshi/byte rate.
Each block will vary regarding how many transactions it includes, based on how many transactions are waiting in the mempool and how large they are. On average, it tends towards ~2000 or so transactions per block. So if I see, say, 1500 transactions pending at 2 satoshis/byte or below, I generally assume 2 satoshis/byte is adequate to get confirmed in the next block, though occasionally it can take a bit longer.