I have checked your screen shots, My laptop have 8gb single stick of ram installed and my ram usage is 3.3gb from 7.9gb (currently 6 tabs open in chrome)
I doubt it should be ram issue, as 4gb is good amount of ram for routine works of the laptop
Firstly, could you give a brief history of the problem
1. When did it start happening (was it there since you bought laptop or did it start after installing some softwares)
2. Did you change anything (hardware, drivers etc? prior to the problem)
3. Did you install or upgrade new OS? (If yes, was it upgrade or fresh install? is the OS legit or pirated)
4. Which OS are you using?
5. Check one thing, when you PC hangs, is the HDD led on front of the CPU casing is continuously ON?? or it continuously blinks? or its off? (Tell me the behavior of this HDD LED when PC is running normal and when it hangs)
6. Is issue same on other browsers?
Regarding the low RAM issue, do one thing Try increasing your virtual RAM (Its a feature in Windows that uses some allocated space of hard disk as RAM)
I remember i used to do it in Pentium -II and Pentium - IV to increase performance back in the days
Whatever number you put in the Initial size (MB) put double the amount in Maximum size (MB)
And the number you put in Initial size (MB) should be multiple of 8 (example 1024 MB, 2048 MB, etc)
Take the minimum amount to as large is 8gb and max to 16gb (Do it phase wise, 1gb initial, 2gb max, then try 2gb initial and 4 gb max, etc)
Try this and see, Hope your issue will be solved
NOTE: The allocated space in the hard disk for virtual ram will be non usable for storage. (If you are low on HDD storage, then you will require to reverse it the same way you did it)
Here is the way to increase the Virtual RAM In windows 10
Manage Windows 10 Memory and Speed Up Performance