So I can not withdraw the btc from it.

After broadcasting it: it gives:
18 txn: mempool-conflict

I can't seem to figure out what it means or how to solve it.

Could anyone help please with withdrawing coins from coinb.in?

It's a multisig wallet. So maybe I can't withdraw to one BTC address (then why is the option there?).
Maybe I should use a multisig method. But how?

Hopefully somebody can help.

I can also not import the wallet to electrum. When I insert the keys it just doesn't work.

And a seed is also not anything because I just imported a seed in monero and now Ive got the same wallet, with some history but not my latest balance. Which was quite a lot. It's balance is zero now.
And also with the monero client importing the keys does not work. Or I am doing something wrong.