Vibrations study help please

I'm really struggling with my vibrations module and my lecturer isn't very good. I'm trying to find sources online to help that aren't too complicated to understand (e.g. not a textbook that is for beyond my degree) but I can't seem to find ones that help. I was wondering if anyone had any resources they used e.g. youtube videos/ questions they'd be willing to share. We cover topics like free vibration, steady-state forced vibration, time domain forced vibration, damping... I don't understand all the different equations that are really similar e.g. X/F, X/Y, Z/Y, accelearance, X/Xstat and what they all mean as well as the graphs in frequency domain, time domain, fourier transforms, FRFs...
Any help would be greatly appreciated as I'm really struggling

The obv thing to do would be to ask your lecturer / classmates, as they know the syllabus/difficulties youre (alll) facing ... Is this y1, y2, ...? Mech eng or .... / uni or ...?

Generally the best way to use this place is to pick a few questions youre having about a topic and post what youve done / what youve had problems with and work through the questions in the usual fashion asking about specific parts you dont understand. So what have you covered/what dont you understand about forced and steady state vibrations for instance?

Its mech eng 2nd year at uni. I think everyone is confused which is the problem. Generally I can do problems but only after looking at the answers and attempting them multiple times. I think its more the concepts and where the equations come from that I'm struggling with (the theory behind it.)
I'm not sure the basics were covered well which is why I think I don't understand where the equations come from or which one to use in which scenario without looking at the answers.
We have equations for X/F, X/Xstat, X/Y and Y/Z for forced vibrations with rotating masses, base movement and relative movement and FRF graphs but I think there are just so many similar graphs and equations that seem to come from nowhere that I can't understand the topics.
Sorry it wasn't clear and hope that helps you understand the problem more