What is the correct measure word for 问题 (question)?
These are the standard measure words for 问题:


Normally you would use 个.
If there is a stream of questions you can use 串, for example 一大串问题.
If there are a couple of questions, you can use 些
If you are talking about kinds of questions, you have to use 类, for example   这类问题 (this kind of problem)


件 is used, but not very often, even in writing. 项 is not a standard measure word for 问题, but it can be used when talking about problems (for example software problems), not when talking about questions.