Gta 5 Ps4 friends adden?

And although I have installed by the rockstar side Gta 5 and I wanted to help a friend at Ps4 at a heist but I can't adden him as a friend. How can I solve this problem

So you can't add him as a friend via Ps4?

Oh sorry I forgot to say that I'm playing Gta 5 on PC

On the pc, I have no idea.

Of course that will not work. Crossplay between PC and PS4 is not possible with GTA 5.

That's obvious. I thought they both wanted to play on the pc