Baking Adventure turned into Baking Fail #3

I woke up today and I was planning to finally make a nice vanilla cake and the filling would be a vanilla buttercream with strawberry pouree or like a coulis. A couli is like a thin sort of jam but it’s taste much better than store bought jam and it has a different texture. I’m really good at decorating cakes but I was still looking for the perfect vanilla cake recipe. I found one and I baked it. I mostly ever bake cakes because my family is small and my parents don’t really like to eat sugar so basically I am the one who eats the sweet stuff... but I do get some help from my little 4 year old brother. So after I baked the cakes for about 40 minutes which is the normal time for cakes they weren’t done because they were still completely raw except for the outside. I let it cook for another like 10 minutes and it was still raw but the outside was cooked but not the inside. I got confused since this never happened to me since I have baked SOME cakes before. This was a new oven and wasn’t even that old because it is one of the new ones that came out a couple of years ago. I cooked it for about 20 more minutes and it looked ready but when I inserted a toothpick the inside still was raw. I looked up on google why it was happening and it said to just put aluminum foil on the parts that aren’t cooking but I was out of that. I looked up another reason and it said that my oven was too hot and the outside was cooking faster than the inside but the normal temperature was 350 degrees for a cake. If this happens you have to invest in an oven thermometer which tells you if your oven is off or over some degrees and I still haven’t got it but I have to invest in it because it will help with my baking. I decided to make a new batch of cake but it did the same thing. I just gave up because it has taken me like 5 hours and I got frustrated. I tasted the outside of the cake and it was REALLY sweet and everything just turned into a fail. The rest of my day was bad and next time when I’m trying different vanilla cake recipes I am going to make a smaller batch of each different recipe to see which one is the best tasting and not too sweet. 😰😂