Hello. I got recently zxr 400 and it was bit slow to start usually, but now after it's been sitting for a while I can't get it to start anymore. I charged the battery couple of times, but it doesn't help. What could I do?

You're going to need to give more info than that I'm afraid. So the bike started when you got it but now it doesn't. You say you charged the battery a couple of times. Did any of the lights work after it was charged? Headlights, indicators, lights on the dash? Do any of them work now? If the answer is 'no' then it could well be a knackered battery, which isn't holding a charge. You need to try a healthy battery.