4/3 might be a little chilly in 55 water, but with gloves, boots, and possibly a hood it should be tolerable. I tried on a Decathlon suit once and it was so stiff and oddly shaped I couldn’t move in it. I’d buy a used one by a proper brand before Decathlon. If you want new and have a few extra bucks to spend, Quiksilver’s Syncro line is decent entry level gear, I’ve got the 4/3 back zip, 7mm boots, and 5mm lobster claws which have served me well enough.
As for the board, soft top would be the safest, floatiest option.. but an epoxy hardtop will feel better, last you longer, and allow for more progression. I’m a heavier guy and started on an 8’ Torq that was around 65-68L or so. If you can find a used Torq, NSP, Bic, etc in that length/volume range that would be a great first board.
If you’re standing up first time out you’re way better than I was. Sounds like you’re ready to start working on your pop-up and turning down the face of the wave. One of the toughest parts of surfing is just learning where and how your local breaks in certain conditions, and how to position yourself accordingly. I still get caught off guard and smoked by set waves because I’m chilling too close to shore. Better to be a little further out and off to the side and miss 1 or 2 waves, than get stuck in the impact zone and miss a bunch then have to fight to paddle back out.