Another stupid question, if i'm playing in the scale of Fm, do i have to write all my chords with only the keys that the scale of fm has?

No. Keys are something that establish a general sense of tonal "gravity". They are not straight jackets.

but what about the melody, it does have to stick to the notes on that key right?

No. There are no absolute rules in music. The melody usually follows the key notes, but it's common that the melody modulates away from the key notes for a while. Anyway, don't limit your creativity with rules: they're meant to help you, not limit you. As long as it sounds good, it is good.

Yeah, you're right, i keep on getting limited by this 'rules', ima start to ignore them a bit more

And minor keys are problematic. In Fm you can equally validly write a scale

F G Ab Bb C D E F

or

F G Ab Bb C Db Eb F

Sometimes the first is know as melodic minor ascending and the second melodic minor descending.

The "melodic" is added because you can also construct a scale from the chords that you use: since you'll likely use a C chord and Bbmin chord, you get retroactively the scale

F G Ab Bb C Db E F

but you would never play that. Unless you live around Constantinople, and then you'd call it "C Hijaz".

Victor.

and once a key is established, there's nothing that prevents one from moving to another key -- back in the golden age of songwriting 3 keys in a 32 bar song was fairly common. There are methods you may find referred to as pivot chords for longer key changes and backfilling/turnarounds for briefer excursions.

pop music often 'violates' all sorts of rules about major and minor chords (which can be explained away with key modulating, but honestly sometimes it's just twisting a chord) (the Breatles were masters of this change) and dominant chords are commonly thrown about because the music we've been listening to has been doing it all our lives (and way back when some guitar players added some color by using chord shapes they knew)