Why do you think that you're using "too much RAM"? "100% CPU usage" isn't at all the same as using "too much RAM." With respect to your computer "freezing," rather than looking at the "Memory" column in Task Manager, you should look at the CPU column and sort that so that the higher numbers are at the top. What are the processes that take more than a few percent of your CPU cycles?
I don't know where you copied the last paragraph in your question from, but this sentence is useless advice: "You can close processes that use too much memory or simply make note of them to keep an eye on those programs." How do you know how much RAM usage is "too much"?
For RAM usage questions, look at the "Performance" tab in Task Manager instead of the "Processes" tab. Look at a time when you think you're using "too much RAM."
Then click the "Resource Monitor" button on the "Performance" tab of Task Manager. When Resource Monitor opens, click the "Memory" tab and post a screenshot of the bar graph at the bottom. See directions here: https://answers.microsoft.com/en-us/feedback/forum/fdbk_commsite-fdbk_getstart/how-to-include-a-screenshot-in-your-post/2594b08e-32a3-476a-85a6-b021181be7e4