You just bought the Sim… Some of us are here from day one last year and we still tuning settings, GPU, etc. to keep or get good results.
What you need with MSFS is first : Patience 
And a lot of reading if you got the first thing above.
For a (very) good start with your Index, I suggest:
If you don’t have the patience, then, I’m sorry it’s not for you, but you’re missing something great 
Edit : The sim need a lot of optimization, and Devs work on this.