Hello! When I put the mesh in the studio, I get a white part

There are problems with it as well:
- you must not join the body with the garment until the latter receives weights, uv_1 and vertex paint;
- a dress and a nude body behave differently. So your dress must receive data from a dress of similar length, not a nude body;
- dresses are vertex painted with two colors, its best to transfer vertex paint;
- you must transfer weights, uv_1 and vertex paint with Nearest face interpolated instead of the default option. Right now the mesh will morph like crumpled paper;
- Right now some uvs are in the space meant for shoes;
- All parts of the body covered by clothing must be deleted. The garment's uvs must go in the freed space. Bigger uvs = better quality;
- loose sleeves will give you a lot of problems;