Hey! Your letters are starting to show a lot of promise, nice work
As far as over/underturns go, they should be mirror images of each other. A good way to work on this is (at the start of a line) to turn your paper upside down and draw an overturn to the best of your ability, then turn the paper back around; this is now your underturn exemplar for that line. Keep working on getting both of these closer to an external exemplar, as your own work will only reflect your current ability; but this is a good way to keep both forms similar to each other. This will also help to open up your double turns too, the underturn exit to these is also tight.
One of the most important aspects of drills is to always be appraising the work you've just done. At the end of each line of practice pause and compare what you've just done with your exemplar, are your ovals (for example) too wide, too narrow, off slant, too boxy etc? You can even mark things you notice in pencil. Then go on to your next line armed with that knowledge and try to improve upon one of the things you picked up on in your previous line. This ensures you're not just reinforcing problems. It's more beneficial to do even just one line of drills where you've carefully considered your forms than a whole page repeating mistakes.
Finally, if you don't already,
date your practice sheets! It's fantastic to look back over them and see how far you've come.