What is checksum used in BIP-39 and what is it for? I dont trust programs that generate 12 words,
Everywhere I read about cryptography , all those smart guys say that humans are a terrible source of randomness. We are always trying to make a pattern or something like that.
If you want security, and don't want someone to brute Force or to somehow discover your keys, you definitely should try some reliable program to generate your seed/keys. That's the most common advice i see out there. As I am not a genius, I just follow it
You can help me? How can I convert my 12 words that I chose myself, from a list of 2048 words, into a wallet?
https://iancoleman.io/bip39/
In this website you can put any 12 words ant it will generate thousands of addresses and privatekey for them
Use it only of you have an airgapped (offline) computer, otherwise there is a small risk that someone may be watching (if infected computer).
For educational purposes, try your words there ... If checksum fails, it will Tell you.