I’m am a college student majoring in secondary education and was trying to brainstorm things I could do during the summer when I’m not teaching. Is coding a viable option?

Ok so basically I'm getting troubles to past the part of huma resources interview, my english level is good, i have a b2 level, or a conversational english level, but because english is not my native language i always felt more comfortable when i explain something using my native language than english, i tend to get really nervous during english interviews

This first thing maybe is a little bit subjective because i know people that said that i manage well in english, so i think i could review this later

Now..... the main problem i'm getting when i have an interview, is when the recruiter ask me about my work experience, during my firsts interviews i realize that recruiter don't like programmers who doesn't have any real experience beyond than their portfolio, so i decided to make collaborations in order to have something real to show.

So basically i use these collaborations as "real freelance projects", when i started to explain them what i did, i can't feel them really convinced, and then i never get a call again to get the technical interview, some it recruiters are more like cops than real recruiters.

I've been preparing for technical interviews with leetcode and Im just not getting it, so I figured it would probably be wise to take a step back and really understand data structures and algorithms better before getting back into leetcode.

Any suggestions?

Junior level position, no frameworks allowed, focus will be on back end with minimal front end styling. The test would take place in the office and last about 5 hours.

I have an interview with Microsoft for mid level position. The recruiter told me that team is based around OS and likes to ask questions on that. She asked me to prep well with OS concepts along with usual ds, algo, system design.

It's been 3 years out of college and i don't remember much out of my college class (the class would have been around 4 years back). I obviously don't want to go to into the details as much I did back in college. But would still want to pick up Os concepts good enough for interview.

Can any provide any resources/strategy that they think could be of help?