Flutter vs Android

Planning to join the mobile development course but don’t know which program is best flutter or kotlin?

I have about 7 years of mixed Android and iOS native experience (worked at a startup as the sole mobile developer) and now working with flutter full time. It's funny how everyone is suggesting native over flutter because it's 'it's less of a hassle' while that's definitely not true.
You can indeed run into problems that can only be solved natively, but that's very rare nowadays considering flutter is somewhat mature. Worst case you will have create your own package and write some native code.
I would chose flutter over native if I would start any app today (I do actually want to start another project next month). So I advise you to go with flutter even if you don't have any experience.

Depends how quickly you want to get to market and also how complex your mobile app is

With flutter you can hit both Android and IOS users with one codebase - soon you'll be able to access web app users as well .

If you're building a mobile app to capture and receive data or build some messaging or social media platform then 9 times out of 10 Flutter would both be okay and IMO more easier to use, but if you want to do something a bit more complex like a mobile game or an app with sophisticated 3d animations you may want to stick to native