Lemmatization. How to lemmatize Russian and English words (Lucene and Porter's algorithm are not suitable)?

Question

Algorithms

Hello! It is necessary to lemmatize Russian and English words. Lucene is not suitable as it is a university study assignment and there must be some sort of algorithm. Porter's algorithm is also not very suitable, because those implementation options that I found and tried to do myself did not work satisfactorily. Can you advise something? Thanks in advance.
PS I'm programming in java and c#, if it's important.