Bandit GSF 600 problems

Would like some advice. Just a little ahead I am quite a layman. Although I have a good technical understanding but rather in the electronic field. And that’s when I got a bandit GSF600 (with throttle because of A2) a year ago. And at first it went really well and I was very satisfied. Bite on a few “little things” e.g. Is it after a longer standing (from about 2 weeks) quite difficult again or dies again at the same time, If the motorcycle was only a short time off (until about 20 min) she also went a little harder. I didn’t mind that yet. Now, after I got her out of the garage again, the same problem was like last year. Dies after a few seconds. After several attempts she ran and I turned a small lap and I still don’t have the full power even after about 20min drive and the sound of the machine was also a bit dull and not right. What do you think? Workshop or do you have tips for me what I could try? Thanks in advance for the help