There are various places to learn but it's tough to actually master the concepts.
The only way to do that is practising.
The goal of practising is not copying or solving problems. It's about learning from them.
Never copy code!!
Have a pen&paper, try to somehow find the relationship between the problem and some algorithms you know related to that concept. If you could actually draw out a structure then it gets easy. The coding part is not an important task at this phase, sometimes the complexity might be heavy but it's your creativity at least.
Having a decent understanding of algorithms or data structures won't fetch you what you expect.
Youtube channels like aditya verma, tech dose, abdul bari, striver have already made so many great videos to learn from, do check them.
The people who are good in dev I recommend them looking for the SRE/Product Engineering roles as their hiring processes are more dev centric.