Some online and free books can help, whereby you can check which grammar you need - gender, conjugations, the 6 cases, verbs of motion, declension of numbers, etc. ;
https://learnrussian.rt.com/grammar-tables/ not just the 'grammar tables' page, but also 100 lessons.
Also: http://masterrussian.com/nounsandcases/gender_and_number.htm and I recall many more pages.
Otherwise a text book or a small grammar book: https://www.bookdepository.com/Essential-Russian-Grammar/9780486273754 for $7.613 Chilean dollars/pesos