How to set up Firefox to work fast?

Question

Debian

Linux Mint 17.3 Cinnamon 64-bit
kernel 4.5.1
Notebook 2009 ASUS K50-In
Pentium Dual-core CPU T4200 2x2GHz
4 GB + swap on SSD
GeForce G102M
1 SSD INTEL 530 Series 120 GB
1 HDD 500 GB
The system costs, of course, on the SSD, on the HDD home is mounted.
PROBLEM: Firefox is
terribly slow! especially on video playback.
The computer has always worked properly, a couple of years ago it had Windows 7, everything was flying. Everyone loves Linux Mint.
1. installed Orthodox Debian - the same in all DEs
2. mounted home on SSD - the same.
3. I already googled - disabled all plugins - does not help.
4. cleaned both the cache and cookies, turned off the profile - the effect is the same.
5. next to the staged Opera flies.
6. even with one open tab and one browser window in the system, the same brakes.
7. there is an ad blocker - it does not save you from brakes, turning it off does not help either.
And not only the video slows down, often opening new tabs and writing text occurs with a delay.
Is it purely a browser problem, a computer problem, or is it a conspiracy: the Internet is forcing me to buy more and more new hardware ???

Answer 1

This is a conspiracy.

Answer 2

No way, browsers now need from 8G of memory.

Answer 3

I use this , ublock, https-everywhere and firebug.
Works 2 times faster (subjectively).
But the specifications on the laptop are higher.

Answer 4

There is a feeling that the problem is not with the fox, but with the flush.
And try to run the fox through the terminal, maybe errors will be visible. Let's shed some light on the problem.