Macbook air battery losing charge fast

I have the macbook air early 2015. Up until a year ago, it worked perfectly, but then it started to loose charge when not plugged in, and now it can only hold for about 10 min without being plugged in. The battery doesnt loose charge and get to 0%, but the mac turns off at around 80% charge, and when I turn it back on (when plugged in) it charges back to 100%. The battery says "service recommended", and has been saying that for a long time. I read online about battery cycle count, when it first started, but the cycle count was low for a simple bettery-is-dead-issue. The count on the battery is only 766 now. (should go to 1000 according to apple).

Do you have any idea of what is wrong? Will it be fixed it i get a new battery or is it a hardware/software problem?