"Matters" (the noun) would be "affairs". Things that "involve" it or "concern" it. Simply, "things" (objects, feelings) that are about the heart. Matters (the verb) could be "important": All that matters is your safety. (Your safety is the most important thing). It really matters to me. (It is really important to me.)

"Matters of the heart" is an idiom that refers to all those things that have to do with your heart. Such as feelings, emotions, passions. The speaker means that - as always happens with all those things you apply your heart to (like falling in love, for instance) - you will know when you''ll get across the right job for you. You will be "magically" aware that that job is the very right one.

Maybe means"the thoughts of your minde when you meet in trouble ".

"matters" here is a noun. As with all things to do with the heart, .... . Maybe more common as in "All that matters is that people have fun." All that is important is that people have fun.