Hello!
I wanted to ask if someone could help me understand why my film has these dark spots. Was it a mistake in processing? Or what could be the cause for this?
Thank you in advance! 
Kinda looks like light leaks to me. The pattern of dark spots would make me guess that the film roll may have been a bit loose and been exposed to light on one side. Could be something else too of course.
Was the film spool tightly wound when you put it in and took it out? If it was loose, light may have crept in from the sides, especially if the lighting conditions were bright.
@valealvarezd, please tell us if you used old film, new film and if you developed it yourself or by lab (the number sticker hints at lab development).
If all your films (that were in the same camera) have these issues, the camera might be the thing to fix. Cameras of a certain age have foam gaskets that tend to loose elasticity and get gooey instead.
I used my Seagull 4A, with a new roll of film and it was developed in a lab. I used my camera afterward many times with other films and it worked just fine, so I don’t think the camera is the problem.
I traveled with that film in my hand luggage, could it be caused by X-Ray? (Even though the other film I traveled with did not have any problems).
Thank you again for the help!
Difficult situation. All things being equal, the film might have been damaged before you got it or afterwards, in the lab… Not all films are similarly sensitive to x-ray…
Absolutely, it could be X-Ray damage… had very similar damage from a roll of black and white that was in my carry on, while other rolls were fine.
Thank you anyways for the help!!