Repeats

I would use multiple endings (ie ending 1 and ending 2), with ending 1 being from bar 20 to bar 40. Repeat back to bar 5, then the second ending will start at bar 41. may look a bit awkward as endings are generally only a few bars, but it will work.

Alternatively, you may want to consider not using a repeat at all, as you are only re-suing 15 out of 40 bars (bars 5 to 20), but it's up to you.

For help using codas, check out https://www.youtube.com/watch?v=04XTa6IrzGg - it may help you find where your coda is not working as it should.

For help in using multiple endings, check out https://musescore.org/en/handbook/volta.

DS al Coda is fine but where you want it to jump to the Coda you need to either use "To Coda" instead of just the Coda sign or you can place a Coda sign but you need to change the properties of the sign (using Inspector) so that Marker Type is set to "To Coda" and label to "coda". Each mark can look like anything you like really but must have a unique label and its Marker Type must describe what it does. With this score, mind you, since you are already well into the third page you might as well just write it out in full.