你好!∩_∩
呃..“我有不会的题时”应该不是个完整的句子吧,可以看成时间状语从句.
可译为：
【When I have a problem/(some problems) which can't be solved by myself,..{后面加你要讲的话}】；
或者【WhenI have a problem/(some problems) beyond(s) my ability to solve,..{后面加你要讲的话}】.
但愿我没理解错..希望能有帮助.