If I'm bisexual and have a muslim friend that doesn't know, are they still sinning?

Homophobic and islamophobic, please scroll this post.

Hi, sorry for eventual mistakes english isn't my first lenguage.

I have a friend that's muslim, they live in Algeria, we were talking and somehow this discussion came up. They asked if i was straight, but i lied, and said i was. I wasn't scared or anything i just didn't want to loose my friend, but i don't want them to sin because of me (he told me it was sin to be lgbtq+/ he didn't want anything to do with lgbtq+ ppl, he's heavily against it). Do they sin because I'm bi even if they don't know i am?

If yes, i will tell them.

If not, i'll keep it to myself. Please help me out here.