This deformations appeared in this 3D round model that I'm trying to create After creating a 3D sphere, and stretching it out. I also created spaces with the boolean method for the wheels using other round shapes. Immediately after creating these spaces, these deformations started to appear. What should I do?
If possible, I would like to receive a simpler explanation, since I'm still a beginner. But if its not possible, it would still be very much appreciated if you help me.
You are probably using the "Subdivision modifier" applied to the car mesh.
You should learn how to control this modifier (it's one of the most complex things in 3d software). Here some basic info: https://docs.blender.org/manual/en/latest/modeling/modifiers/generate/subdivision_surface.html#control

The easiest way to go on with your work is to disable the subdivision modifier and work in a "low poly / flat / shade flat" way. 

Once you mastered basic modeling, you can try experimenting also the "subdivision" things (here one of many tutorials you'll find on youtube: https://www.youtube.com/watch?v=xmIIIcCUm8E)