From your comment:
I’m just wondering is there any general way to avoid using man over and over again in a sentence.
I don’t think that repeating man is a big problem on its own, but I do think that phrases become clearer and more vivid if we use it sparingly. You can (almost) always go ahead and talk about the actor, the person that is hidden beneath the stealth cap of man. In many cases it is — you! It is incredible how many people say man, but actually just mean I. If this is the case, you should better say
Wenn ich solche Goethe-Institut-Prüfungen machen will, muss ich bereits wissen, auf welcher Stufe ich bin.
or (avoiding one of the three ich):
Um solche Goethe-Institut-Prüfungen zu machen, muss ich bereits wissen, auf welcher Stufe ich bin.
But maybe you really wanted to speak about other persons. You could then try to find a general (or, pars pro toto, just typical) name, category, profession etc. that describes these persons
Ein Schüler / Student / Interessent / (maybe context suggests even more), der solche Goethe-Institut-Prüfungen machen will, muss bereits wissen, auf welcher Stufe er ist.
And finally, you can use at least jemand or a relative clause with wer, and you will at least avoid the repitition, and have a personal pronoun in the last part:
Jemand der / Wer solche Goethe-Institut-Prüfungen machen will, muss bereits wissen, auf welcher Stufe er ist.