I really struggle with making frosting.

I moved to a different country and the thing I miss the most is the cakes, cookies, and desserts of the USA. There is a completely different dessert culture here (Latvia) and most desserts are extremely soft, and extremely moist cakes topped with gelatin and fruit. There are some chocolate cakes too, often with sour cream or yogurt as frosting.

My goal
So I've been trying to make my own cakes following popular recipes online. I don't know what it is, but they miss the mark. I'm either doing it wrong, or I'm noticing a significant different between homemade and box cake mixes, grocery store sheet cakes, and betty crocker frosting. Honestly, these "worse" recipes are my goal since I grew up with them.

Result Issues
Specifically, let's talk about frosting. It usually turns out flat, and with chocolate frosting, it turns out really pale. It tastes sweet, often too sweet, but weird and like there's nothing else to it. For this frosting, I've followed this recipe and recipe.

Ingredient issues
These seem popular, but I don't have enough baking prowess to know if they are good. The other issue is that my country does not have the same ingredients.

  • We do not have baker's chocolate, so I use dark chocolate instead.
  • We do not have vanilla extract, so I've tried vanilla sugar and vanilla paste. We also have 8ml of "vanilla flavoring/vanilla aroma," but I don't know what that is. I've been wanting to buy a couple vanilla beans though so that I can make my own vanilla extract.
  • I typically make my own powdered sugar by grounding down granulated sugar (we only have one company that makes powdered sugar, so it's quite expensive and only sold in small amounts).
  • Butter here only comes unsalted, so I try to figure out how much salt to put in if the recipe doesn't use unsalted butter.

Equipment
I use an old handmixer on high. There is a turbo button, but I've never dared to touch it before.

Is it okay to substitute cocoa powder for an equal weight of dark chocolate? I did this once.

Are there any other guidelines or things to remember regarding these recipes? Perhaps differences in store-bought things and homemade products? Or better ways to use the ingredients that I can find here? Thank you :)