I studied Russian for several years, and visited Russia several times. During my visits to St. Petersburg, students from the US, Ukraine, Russia, Poland, Croatia, Serbia, and more were all learning together. Many friendships were born, and I am shocked and sad to see the war tear people apart.
I can't overstate how valuable this site has been. Basically, it converts to or from any form of any word. After all, when a word is in a different form and you don't know the original, you can't look it up in the dictionary. It also helps with irregular changes. Does a bit of translation too.
I never found a great all-in-one chart, so I made one myself.
(I think it's worth getting used to grammatical terms in the language itself:)
* Fun fact, there remain vestiges of some otherwise-extinct cases: