need help with the mesh

Hi. When you import a blend file, s4s splits it along uv island borders. Since your uv_1 is very torn, the mesh is split in many places as well.
- separate the garment from the body;
- select the garment, create two vertex groups, naming them Sleeves and Torso. In 3d view select sleeves, assign to Sleeves. Invert the selection, assign to Torso;

- clone an export a chemise, append it in the scene with your garment, select arms, covered by sleeves, separate them. Name them R_arms and R_torso;
- transfer uv_1 from R_Arms to Sleeves vertex groups, apply. Do the same with R_torso and Torso;

- once done, dont forget to delete vertex groups you created

In s4s main menu click on CAS, in the search bar type in « chemise », choose one swatch, click Next, name it Reference, save somewhere. This process is called « cloning ». Then export the mesh and append it in the scene

Mauve you're a lifesaver thank you! I used the EA nude body and separate it to (torso, L arms and etc) to fix the entire uv1, instead using the chemise. now the UV1 it's doesn't look messy.