I forgot to mention that I'm not that good at this technical stuff but I can figure out a circuit from schematics. I just haven't dealt with op-amps before.
I have no idea how I would connect it with my SCART-cable
Here's the SCART-pinout of one of my video games consoles (SNES - PAL):
This "feeds" the SCART-splitter but the TV doesn't get enough signal power from some of the RGB-signals I guess?
Looking at the picture of your SCART plug,it seems to have its own built in terminations connected to the red,green & blue pins.
If your TV has internal terminations,& the scaler has,as well,you are looking at not double,but triple terminations.
If the terminated SCART is the standard for these devices,we can assume the TV will not be internally terminated,so such a connection would give the full standard level when connected to it alone.
Luckily for me,I don't live in Europe,so have had minimal experience of the horrors of SCART plugs!
If you have just paralleled up two SCART connectors,& they both have internal trminations,you are back to triple termination.
My suggestion is to remove the 75 Ohm terminations on red,green,& blue on both SCARTS.
You will then get your termnation from the scaler alone.