Done and dusted, I overdid it

How must I improve ? Well this was me just spamming new game one after another. Amd it fried my brain......lest, I want to improve, I had dropped to 450 elo and I was 600 elo before, itngot a bit further 700...and then I stopped playing it yada yada yada....now, for few months I started again.....and it's droppng what is happening ?

How must I improve ? Yt ? Books ?