I do not know the real reason for that and I believe that my posts are valuable and they were deleted by mistake
<-- You can see how valuable your posts are by your merit score.
It's the first I've done: to have look at his merit score. the fact that he has 250 merits has made me suspect that he got them airdropped.
OP, you seem to believe what you are saying. Do you really think they have been deleted by mistake when you aren't getting any merits at all?