How can I remove the negative trust?
You can't. The only person who can remove it is the same person who gave it to you. I don't think he will remove it because your case is ponzi (stealing)Quote
'coz I want to continue in my signature campaign and I don't know how to remove it 
Unfortunately there is no way you can continue unless a campaign allows negative trust members.Quote
And how can I know if it is in LEVEL 2?
See trust list. You will see their level.https://bitcointalk.org/index.php?action=trust