Your pentium is running at expected speed.  It is not bad although slower than Intel core.  An ssd will help you boot Windows faster but not much help doing tasks.  If you do only one task a time not opening multiple browser tabs same time, 4 Gb is minimum.  Upgrade to 8 gb will help in your case because you are already using 90% of 4 GB as shown.  Ultimately these upgrades do not solve the problem of slower pentium, but will ameliorate some feeling of system slowness.
Hello, I have an Inspiron 3277 AIO that has been becoming slow and lagging in many ways. I talked with the store I purchased from and they told me to upgrade the RAM from 4GB to 8GB and to get an SSD (either 256GB or 512GB).   I want some honest opinion whether I should upgrade the whole thing or just to get a new computer. Oh, I do have limited funds.   Please do advise me! Thank you.
Upgrade or buy a new computer?