Laggy flash game

I have a Toshiba laptop, 6GB RAM, think its dual core i7 something. Just upgraded to Win 10 (or some months ago).
Here is my problem. I play a small flash based game (I have installed flash), but it takes like 15 minutes before it lags like crazy. I dont have many programs running and I have tried to disable a lot of stuff that I dont need.
I have also done a clean install 2 weeks ago. This did not help at all.
And its not just the game, its Chrome as well. If I perform a speedtest my upload speed is 0.8 (whilst DL speed is 70-90 mbits).
I dont experience troubles with our wifi/internet. My phone is connected and it works well on my laptop (usually).
I have no idea whats causing this game to lag (itself) and also use almost 30% of the memory.
It worked fine!!!! before I installed windows 10, so there has to be some sort of connection here, but I am not able to figure it out.
I am not soo techincal, but I can take instructions or read upon something if thats needed.
I have 450 GB free harddrive space.
Its driving me completely nuts. I can not stand lag/or when stuff does not work as they should. And also, when I cant see no reason.
Has anyone experienced something similar or have a useful guide or some useful tips & tricks for me?
I hope have given you enough information btw.
Thanks!:)