how can i trust this secret key when someone else is telling it I want to create it manually and there is no option to do so. I said for now you have to trust them, its new yet soon you can do it manually too.
If there is way to do so please share a link or wallets providing this type of facilities.
There are some relatively reputable hardware wallets that allow you to generate your seed manually instead of having to trust built-in true random number generators. For example, in Coldcard, there is an option to generate seeds using dice rolls, coin flips, a combination of both these methods, or a combination of all manual methods with the hardware wallet's own RNG. Upon each roll, you will be shown a hash of the result of each roll, which you can verify manually (not for your actual seed but for testing purposes) by following this guide:
https://coldcard.com/docs/verifying-dice-roll-mathAs for passphrases (sometimes incorrectly called a 25th word), you can generate them easily with dice rolls completely offline without needing to download any software or buy any hardware. For example, you can download some of the wordlists presented here
https://www.eff.org/deeplinks/2016/07/new-wordlists-random-passphrases and generate your random passphrase using a set of multicolored dice.