Does a native mobile app need to be essentially built as a web app and adjust the responsive settings? Help

Hey all. I’ve invested many months working on a native mobile app intended for iOS and Android. I might have messed up really bad… Please help me.

I did not do any responsiveness at all whatsoever while building my app’s complex features. I essentially just got it to work and did all the heavy lifting with developing the features first. Yeah… bad mistake. Anyways. Now as I near the end of the functionality aspect… I realize this big issue. Especially as I know that the appstore requires your app to also work well on ipads. While I built my app, I had it at a fixed width of about 415px. You can imagine how everything else is right now. Can someone shine a light on how this would be done? I was thinking I might have to fully re-organize my app into a web app, and then do the responsive features so that on mobiles and ipads it looks as desired by mimicking regular mobile responsiveness… but is this the only way? I’m asking since as I mentioned I stupidly built the entire app as a fixed width of 415px. So if I want it to work for ipad, I will inevitably have to stretch it outward. I’ve not found many useful responsiveness guides for native apps sadly. Please help.

Another question, if I end up having to essentially make it a web app, will I need to organize everything into a full-width desktop screen or would re-organizing it all into something slightly smaller make it simpler by any chance? Thanks a lot!