Tried to root now file manager is empty

Hi,
I'm not very tech savvy so please excuse my lack of knowledge.
My HuaweiY530 has been through a lot of manipulations to extend its storage with a SD card. I never got around to creating a partition but my phone was rooted and used link2sd.
Last week a friend tried to create a partition but couldn't. What it did is make everything disappear from my internal file manager. It looks like there's nothing on my phone. When I create a folder it doesn't appear anywhere. I can't download a file, can't save a picture...
I can take pictures and install apps from the playstore.
Not knowing what to do I did a factory reset yesterday. Nothing changed.
Of course, no way to install towelroot either.

What's going on ? What can I do ? Please help !