Why is Pokemon Go works laggy and terrible on HTC M9+?

[AC Question]

I own an HTC M9+ and I play Pokemon Go, It works so terrible although HTC M9+ Is quite a good phone. Its very laggy in the inside of the game when I browse in my pokemon's and sh*t. Anyway, since the new update came out it works even worse. Is worked fine when it comes to location and using GPS and 3G but now its showing me that I'm somewhere that I dont like 30 Feet away from where I am standing and also if I walk like, Couple of meters the game only walks a little bit and then stops and its allways showing the Loading Pokemon Ball in the top corner. If someone have any idea how to fix it please answer!!! Also to note: I have version Lolipop 5.0.1 and I want to update to Marshmallow 6.0 (Mybe that's the problem..) but my phone tells me that no new updates available [?], Please if any one knows what to do about both two problems answer! Thanks.