Don't call yourself stupid! You only had one week and as you said, gamedev is hard!
For the continuation, it would be good to have things like a titlescreen and buttons and stuff. What came to mind in my recomendations would be that the player controls a gardener that has to plant and water plants while destroying bad plants.
Then you could add time limits, high scores and all that stuff. If you are a beginner, I recomend just joining as many game jams as possible and create different games rather than focusing on one game. That way you'll learn best and one day will be able to make a big, full game!
Btw the artstyle is absolutely fantastic and something you could perfectly improve on!