You have a game ban, not a VAC ban.
You aren't allowed to share your account. You are responsible for what your friend does with it.

引用自 o_Dester：

Hello, I was banned by mistake. It wasn't me who was playing at that time, but my friend. I forgot to log out of my account when I visited him.

1 game ban on record | Info
3 day(s) since last ban

account security is your responsibility and its irrelevant who used the account. The account was caught breaking the rules. As per your profile, you have a gameban and not a vacban, irrelevant what it says ingame. So go to your profile and click on the info button next to your gameban