It sounds OK but I think 'am' sounds better than 'have'. 'A' isn't necessary. Do you want to put 'even' in front of 'sure' or in front of 'have' or 'B2 level'? If you put it in front of 'sure' it is your certainty that is questioned. In the other two positions, the level is questioned.

Sounds ok. You can also say “I am B2 level”