What should I do with my mother and sisters who imitate people and their movements and voices for fun, and rush to judge religious matters without knowledge?

Mimicking the voices and movements of others to ridicule or belittle them is a form of backbiting (Gheebah) which Allah has forbidden, as He says: "Woe to every slanderer and backbiter" and "And do not backbite one another." This act is considered like eating the flesh of one's dead brother. The Prophet (peace be upon him) warned against backbiting and slander. A Muslim should guard his tongue and refrain from ridiculing others, for whoever ridicules another will be ridiculed himself. And remember that a word can cause its speaker to fall into the Fire. A Muslim must respect others and deal with them kindly, and spend his time in what benefits him.

As for speaking about Allah without knowledge, it is one of the greatest sins. Allah has made it similar to polytheism (Shirk), and He has promised those who invent lies against Allah that their faces will be blackened on the Day of Resurrection, because hearing, sight, and the heart will be questioned about by their owner. Therefore, a Muslim must be extremely careful about this.