I think your max is 3.5tonne, loaded, so you will need to take care.
As said above, best to go to a weighbridge and find out how much (over) you are.
Simple answer to "How much stuff?" is "Not a lot, but sufficient".
The published payload for the 2018 model here is 508kgs, which is not too bad on paper for just two of you but:
1. Read the small print in the brochure to see what's included in the calculation and what's not.
2. Bear in mind the weight of any non-standard extras you have fitted, for example satellite dish.
3. Load it how you'd want in loaded for a typical trip and take it to a weighbridge to verify its actual weight.
4. 4 adults plus kit in the vehicle could quite easily take you over the limit.
Worst case scenario, if you can't run it with 508 Kgs, and you have a C1 Driving licence consider getting it up-plated. Some extra cost involved but cheaper tax.