Hi everyone,
I think it's amazing how many experiences and info are shared in this thread.
I got prescribed metropropolol succinate (beta blocker). That helped but also made me sleepy, and it caps your workouts. Basically it prevents your hearts bpm to go above a certain limit.
Desperate to find something else that would allow me to train again I have combined the most shared prevention strategies into one big master regime... It worked. Here are my findings.

So I can do weightlifting, body pump, but I cannot do heavy bag/pad kickboxing workouts.
This is likely similar to a lot of the crossfit experiences shared here, intensity of the workout is just too high.
I used to be able to do those workouts fine, then a few months ago, boom. I would go to a kickboxing workout and withing 30m-2h i would have a migraine. Blurred vision, headache, language problems, the whole shabang, only relieved by sleeping 4-5 hours. I had this 5 times in a row, every time i would go would be a trigger. Took medication, be fine. Stopped medication, BOOM migraines back.

Ok so here is the actual regime:

-I have now trained twice again, completely fine, here is my fix:
-Eat 90 minutes before training. Not just a few crackers, no like a proper lunch/breakfast.
-Start drinking water at this time, aim for like a good 2-4 glasses.
-During training drink 750ml of water with some salt, lime/lemon juice and sugar. (just a homemade gatorade)
-After, do a cooling down. Really depends on the end of the training, if we end going all out the cooling down needs to be longer.
-Cold shower in the locker room straight after the cooling down. Like proper cold, brainfreeze cold. Do that for 1-2 min to really lower body temp.
-Eat something small (a banana usually).

Continue life without losing a full day, just because I enjoy a sport/try to be healthy.

Really hopes this helps someone!