Don't try to fix eveything at once. Just focus on one task and keep doing it until you are pleased with the result - "you are pleased" - don't feel somebody else needs to judge your work. If you are just starting apply what kindergardens are told.. "practice makes perfect" and enjoy the process.
One more to make straight seams: if you have already a 1/4 foot, put a tape on the right side of the machine bed at 1/4" from the needle, then align your fabric to the tape and saw. I promise that you will saw a straight seam.
Good luck and be patient. If you are not pleased and cannot live with it, use the seam ripper; if it is not that bad, be happy and keep going!