Why is my sculpture growing sharp and edgy when I try to (for example) grow an arm from the main sphere? Or trying to extend something? I'm completely new to Blender. I wanted to use it for sculpting, but I came across a big problem that is completely messing me up.

Like I'd be trying to make an arm or some horns, but when it gets just a little off the main sphere, it gets all sharp and edgy and looks stretched? If that makes sense.

But this is a really big problem for me, and there is sometimes where it gets too sharp, that the symmetry breaks and I can't even erase it?

Does anyone know how to fix this? Again, I'm a beginner, I literally don't know much about Blender yet, so sorry if I don't understand your answers I'm also using a PC, no mouse, so not all key shortcuts work.
It seems you are sculpting a 3d mesh without any knowledge of 3d in general. I think you did not subdivide properly the mesh or activating Dyntopo in your paint brush tool panel. That cause a weird mesh deformation due to low face polygons number, a topology problem.Spenting some time in watch some ytube tutorials could be a good star point.