Hello.
I play browser game. Grepolis.
My laptop - lenovo x220, system mint.
firefox (80-90%) CPU
chromium better but also high CPU.

It possible to optimize something to change this situation?

Fan has a high turnover.

No...it's a browser-based game, so you're at the mercy of the flash/java/javascript/whatever-they-use to play it.

flash - rather no. I have disable in firefox.
Maybe I need use a different version java?

No...again, there is absolutely nothing you can do to 'fix' this. Whatever resources that game uses are browser based, and are going to be fairly high in load.

On windows this game better works.

...then play it on Windows.

It could be bad javascript that's chomping your resources. All those ads and other things running on the same page as the game. Resizing the browser to push those off screen might help idle a few processes. Or refresh a couple times until you get an ad that uses less resources. Firefox tends to not use the GPU so chromium might perform better. You can also use a lightweight webkit browser like uzbl (and several others). There's a little bit of a learning curve since you'll mostly use hotkeys to navigate on the webkit browsers. But they're soo much lighter than firefox and chrome and perform better on hungry sites and games.

In terms of java, having the jogl stuff installed helps. It adds openGL stuff to java's capabilities and helps it perform better depending on the game. Package libjogl2-jni under debian. Otherwise the game uses the resources that it uses.