Why I can ask question in MathOverflow and not here (MSE)?
You cannot ask questions on Mathematics Stack Exchange because you are currently question banned. This ban is automatic and kicks in when some algorithm decides that your question contributions are of poor quality, and are not of positive value to the community.
In contrast, you are not question banned on MathOverflow.
Though both sites are part of the Stack Exchange network, they are quite independent (as are all Stack Exchange sites), and a question ban on one site does not carry over to another.
To get out of the question ban you should read and follow the advice given in the Help Center
and also on Meta Stack Exchange
Question bans do not time out, and moderators cannot lift them. The only way to get out of one is to improve the overall quality of your contributions to the site on which you have a question ban. Most importantly, you should improve your current questions through edits. New high quality answers may also lift the ban.
But I'd suggest you go through your current questions and improve them.
Last, but certainly not least, the following two pages are must reads.
Post Scriptum: Make sure you visit the pages linked in this answer.