Thank you for asking the meta question before posting your English question.
Can I post my questions and answers here to check them? Or, how can I find the answers for the exercises?
The first step is to determine the appropriate community for your question. There are several Stack Exchange communities dealing with language, including the following:
You can post any question you like, so long as the question would be of interest to the target community. If you post a question that isn't of interest to the target community, the question is more likely to be closed or ignored.
For example, if you are a native speaker and you are exploring the nuances of zero articles vs null articles, make your case (directly in the question body) as to why people fluent in English would be interested in your question. It might be a good candidate for EL&U. If you are still learning the language and want to know (say) how to construct a sentence set in the present that references an event in the past as well as its continuation in the future, ELL might be a better place to ask.
Either way, go to the community's main page, scroll down to the footer and click "Help". This takes you to the Frequently Asked Questions, where you can find some basic information on what kinds of questions are considered on-topic for that community, and which aren't.
Regardless of where you post, though, search the community for similar questions (the search bar is at the top of the page) and make sure there the question is clear enough that the community has a chance of posting a definitive answer.
It is almost always inappropriate to simply post questions and answers (here or at ELL) simply for checking. You should first think about what the underlying problem is - and ask that. This archived blog post provides more detail.
In addition to the help pages, have a look also at the links collated in my meta post related to questions on hold, especially item 1 there about the ELL meta post entitled "Please, everyone… details".
Thank you again for checking first about asking questions from your textbook. Whichever community you end up posting in, I'm sure the extra thought you put into framing your questions would be appreciated.