first things first. I would apologize to the entire world for the disaster that happened with Windows 10 Mobile. and promise to be fully committed to the next version of Windows on mobile.
2. reintroduce windows to the mobile market with a refreshed windows experience along with a premium built phone such as a surface phone. iteration s can be added such as a foldable version and whatnot
3. withdraw ALL Microsoft apps from Apple and Android application stores. this is to make a statement. to show consumers that if they really want Microsoft services they need to commit to the platform
4. to counteract people's response "there is no developer support", Microsoft should really push developers (money, threats, etc
to make the damn apps. yeah I'm talking to you Google and Snapchat.
5. Marketing marketing marketing. Microsoft already has a great established name with the surface branding. people would drool over a phone of the same build quality
6. Cortana should be updated. I used Google assistant for the first time for a week and I'm blown away. come one Microsoft you could do better