selling issue

hello dear supportive team,

i am selling on amazon from last 1 and half year but what i observed is that amazon just care for themself i am saying this because i have launched almost like 8 products and i run adds for products, i dont get any sales until my account showing negative money/advertisement money. after the advertisement amount shown in the account ,i start getting sales until all my negative amount is cleared and after that when it should be selling for me sales stopped again and again i put add/ppc and then again i got sales until negative amount to be charged. what should i do in this scenario? should i close/stop selling on amazon?