I wouldn't trust simple websites for tumbling your coins. There are CoinJoin software solutions, namely
Samourai Whirlpool and
Wasabi CoinJoin but it's highly recommended to use Monero instead of Bitcoin for your privacy needs. Monero has built-in privacy. With Monero, no one can see the sender, the receiver, or the amount. Every bitcoin transaction makes those 3 things (and more) public.
The most secure solution if you have to accept BTC is to CoinJoin them and then convert to monero. From there you can do what you need to do, even if that includes changing the monero back into bitcoin.
You can find trusted crypto converters (not tumblers) at
https://kycnot.me/ and
https://trocador.app/en/