I just recently got my film developed and there are these lines in some of my photos. Is it my camera's fault, or there were some mistakes/errors in the developing process?
Perfectly straight discolorations like this one usually come from the scanning process. It could mean not calibrated/damaged scanner sensor. It can also mean there is a dust in a calibration area or on the sensor. Could be an easy fix depending on the model.
Streaks often show up in "dense" negatives, as the scanner has the lowest "signal to noise" ratio in those. They are very visible on even surfaces, such as skies.
What scanner did you use? Flatbeds are notorious for that. Good news - you can always rescan.
Before looking at scanner though, rule out the film itself. Try looking at the negative with a backlight from a light pad (phone or tablet screen set to display white background will also work). Do you see those streaks?
Next, try examining the surface of the film (shine light on the film, not through it). If film looks ok, then it is scanning process which introduces them.