Lots of past papers for Higher Maths - recommended by a maths teacher:
https://www.highermathematics.co.uk/higher-maths-whole-course/
https://www.highermathematics.co.uk/
some of my suggestions...
https://www.maths180.com/live-online-tutorials-2019.html
Make a Graph - if you want to see what the graph of y = 2 sinx looks like etc then try out here - very good website:
https://www.mathsisfun.com/data/graphs-index.html
Interesting website:
https://cjmaths.wordpress.com/