First of all, I am not asking for advice about what to invest in.
TLDR: I just want to ask for advice about how to know what to invest into?
Background information and/or irrelevant rambling below:
I have minimal experience with stocks, having only invested €2500 into a pension account thanks to it being a gift from my father some years ago. Early this year I got taxed about €200 for unrealized gains of my stocks, mainly one of them (RHM.DE) and it takes up a little more than half of the value of the stocks I have. At that point in time when I got taxed it was up almost 100% compared to when I bought it almost two years ago. It has now fallen quite far again and as a result is up less than 10% and my gains are €180 so basically the massive gains (if I had sold at the right time) got cancelled from the taxes. Although to be fair I don't actually know if that's how the tax system works, but I do know I was unlucky to not just sell it off at that peak. But speaking of luck, I am still up like 60% overall thanks to another lucky stock which is up 150% (ENR.DE) compared to when I bought it.
Again, I have no sense for economics or financials or investing lol, genuinely just lucky??
The investing I did was based entirely on Merz changing the direction of German defense policy when he got elected where he said his government will heavily invest in defense. Rheinmetall being a German weapons manufacturer, it only made sense (and it paid off for a while) and the Siemens investment I made was just an afterthought in order to not have all my eggs in one basket. I also have other stocks that are up like 60% 75%, 90%, and then get this: a stock I didn't even buy (it was like a split-off of something else, and given to me automatically?) is up over 800% so I still have an overall value of €4000 from a starting point of about €2500 and €1500 gained in less than two years is, of course, and I cannot emphasize this enough, just purely luck lol
I might as well have gone to a casino.
Long story short and reason for posting I'm now wondering what to do with that RHM.DE stock. Because it doesn't seem good anymore and maybe the ~€2100 value is better spent somewhere else? But how do I know?