Mount TV and TV Stand. Unclear Wall

[Lucasdh]

Hello.
We're planning to mount a TV and TV stand weighing around 70kg.
It's a simple plasterboard wall, but here's my problem. I have found a stud in the middle of the wall, but I've test-drilled and searched the rest of the wall without finding any more studs (45, 60, 90 cm and various other distances). I need something more to attach to and don't think Molly bolts are enough to hold everything.
The apartment was built in the 70s. What kind of wall do I actually have and how do I mount heavy items?

 

[Svanteman]

If you've already made a bunch of holes you need to patch up, you might as well cut open a part of the wall and take a look to see what you're working with.
A 10x10cm should be enough to reach in and feel around.
Otherwise, make a bigger hole and insert plywood strips where you want to mount the TV.