I believe the OP is asking how to increase fees when you're withdrawing from Exchanges etc ("BTC Trading Market")... specifically, ones that use "fixed" fees that are way to low for today's fee levels...
Is it possible to pay extra fee when sending BTC on the trading market homepage, which doesn't support mining fee over 0.0005 BTC or more?
=>> I don't know how to find private key in my market acount. (Is it exist? Is it even possible to know the private key from trade maket homepage?)
Generally... No. This is why leaving large amounts of coins in Exchanges/"Trade Market homepage"/Gambling sites is a "Bad Idea"™. You don't have access to the private keys, which means you effectively don't have control of the coins. You are basically trusting the site to not steal your coins. Look at the "Scam Accusation" forum to see how this scenario can end up
[2]
Rebroadcasting a similar transaction with a fee attached will invalidate the one that's waiting. Basically you initiate a double-spend and the new one (with a fee) will get confirmed. Once it's confirmed, the old transaction will be invalid and forgotten.
==>> I don't know how to create raw transaction & others..
You won't be able to do this... as you don't have the private key to be able to sign the "double spend" transaction. Only the holder of the private key can sign transactions.
[3]
Transaction Accelerator from viabtc.com
==>> I didn't try.. but I don't get it. how to raise the priority without pay more fee? And how effective is it? (like can I get stucked BTC in a few minutes?)
ViaBTC TX Accelerator
can be very effective. Although it is not without limitations.
1. The fee must be at least 10 sats/byte. This usually isn't a problem for most transactions from exchanges etc... they generally send at least 50-100 sats/byte transactions.
2. They only accept 100 transactions per hour. These slots reset at the start of an hour. As the network has become very busy lately, and fees skyrocketed to 300+ sats/byte... this service got VERY popular. So much so, that the 100 slots per hour will generally fill up in the first minute of an hour. So it can take a while to get your tx submitted successfully.
3. There can be no "unconfirmed parents" for your transaction. This could be problematic with exchanges. Some have a habit of creating chains of unconfirmed transactions by spending unconfirmed change amounts.
4. You have to wait for ViaBTC to mine a block (and sometimes 2 depending on how busy they are). They're a Top 10 pool by hash rate... and seem to average something like 5-10 blocks per day. So you could be waiting 10 minutes... you could be waiting 10+ hours.
Another option you have is to do a "Child Pays For Parent" or CPFP transaction. Basically, you create a transaction using the unconfirmed output (unconfirmed UTXO) that you got sent from the site... You send this to yourself and use a HUGE fee... so big that it makes the average fee across the two transactions big enough that the miners want to claim both (ie average of 400+ sats/byte). This works because the miners need to confirm the parent transaction to be able to confirm your new transaction and claim the huge fee
).
The formula to calculate the fee to use for Transaction 2 is: ((Trans1 Size in bytes + Trans2 Size in bytes) * BIG fee rate in sats/byte) - Trans1 fee.
Ie.
TransactionA (from Site to You): 0.2 BTC... Transaction size = 226 bytes, fee of only 100 sats/byte = 22600 sats
TransactionB (from you to you): 0.2 BTC... Transaction size = 226 bytes
BIG fee is currently 400 sats/byte
So your calculation is: ((226 bytes + 266 bytes) * 400 sats/byte) - 22600 sats = 198200 sats
Your 2nd transaction then "looks" like it has a fee of 198200 / 226 = 877 sats/byte... but when combined with the first transaction it averages to 400 sats/byte.
The big 'gotcha' with this method, is that you MUST ensure that you are using the exact same (unconfirmed) UTXO that was created by the first transaction. This can be a problem if your wallet doesn't have "coin control" features that allow you to specify which inputs to use. If you get this wrong, and don't use the correct UTXO, you are just creating a 2nd transaction with a massive fee that is unconnected to the first and so the first transaction still probably won't get confirmed.
