I want to make a fiber glass part and it has to be transparent what material,resin,hardner should i use
If you use fiberglass it will be fairly translucent, but not really transparent. There’s a difference.
Yeah probably need to go to acrylic or some kinda plastic to be fully transparent. Although fiberglass comes pretty close.
There are clear casting resins available, or you could try vac forming clear sheets of Perspex. That’s how goldfish bowls are made.
If you give us some more details we can help you more.