Usually, you are not allowed to do so. See https://help.researchgate.net/hc/en-us/articles/14846037644817-Copyright-and-ResearchGate. Some publishers/journals allow preprints. For many of my own publications, I produced "preprint" versions after publication to be able to upload full-texts to ResearchGate.

thanks for your response and the link. That's what I thought, I can only share a private copy.