the answer for a candidate or catechumen who has more question is not to drop out, it is to ask the questions and keep asking until you get answers. for one thing, unless you stay for the length of the time it takes to cover the basics (ideally at least a year, from right after Easter to the following Easter) you don’t know yet what will be covered, and what will be missed. For another thing, you don’t know of outside speakers or other resources will be used to cover what the regular catechist can’t.
For a third thing, you are also there for each other, and asking your question can help another participant. There is no magic number of months or weeks, “it takes as long as it takes” some people will do fine with what can be taught in a year, some people may take years, struggling and study first one issue, then another, resolving problems, doubts and concerns as they arise.