When i talk with linda, it tells me at last that for continuing progressing, i need to change her outfit, but i cant find how.

There should be a "change clothes" option when interacting with Linda.
Also, you might want to take a look at this guide for what to do next to progress Linda's story:
https://docs.google.com/document/d/1RiddNpybmX089L_Ib_91Vdi4R8bLZWPqTnTvz3N5QnY/...