Well, as you're starting with "but", I assume this comment is in direct response to another one.
I'm not sure what you mean to say by using "but how if...?" Are you suggesting a possibility? Then use "But what if...?" If you're asking how something happened in spite of something else, then use "But how, if...?" Without the preceding sentence, I can't really know.
"My exam results" should be the ending for both statements.
For the difference between "were asking" and "asked", it's the basic difference between simple and continuous tense. Again, can't really give a clear answer without context.