I have reading a book myself; more than 90 % of the book is ok to me; but I have some problems on it. Is it ok to ask my questions in a related chat-room? Because I believe that they are so easy, and it seems shameful to me to ask such an absurd question?
Yes, one of the functions of the chatrooms is to allow discussion of problems in a "chatty" fashion that is not appropriate to the Q&A style of main Math.SE. Back and forth discussions often start in the Comment section of a Question and get migrated to Chat.
I frequently have this same problem but I have learnt to ask the question anyway. Provided the question or equivalent doesn't already exist, often the answer is given in a comment rather than an answer, as users are embarrassed to answer such trivial questions. But inevitably somebody later needs an answer to the same question and finds it useful. In fact I now see many others asking relatively trivial questions.
MSE is for mathematicians of all levels and there are as many trivial misconceptions and problems understanding as there are deep and interesting ones. While we of course aspire not to ask bad questions, bad or duplicate question will get downvoted and removed so you receive feedback from the community on what is considered acceptable.
I get the impression some of the more advanced mathematicians fail to appreciate the full extent of my mathematical ineptitude and find trivial questions frustrating but there are other less experienced mathematicians who know more than me while appreciating my difficulty with simple problems and are happy to help.