For someone only bowling 6 months, you are doing quite well. Your average is respectable for your experience. Are you a decent bowler? That is like asking us if the woman over there is pretty. We can't see her and have nothing to judge by.
A few years ago my local association hosted a State Championship Tournament. On one squad I worked there was a bowler with a 242 average. Just looking at the average I would have said he was a "decent" bowler. I watched as he bowled his singles and doubles, (6 games) he didn't break 170. Was he a decent bowler? I would have to say no. He has no idea how to adjust to different conditions. In other words he doesn't know the sport.
Don't worry if you are a decent bowler or not, and don't worry about what others believe. Continue to learn the sport. Your confidence in your ability will grow, and at some point you will know that you are a decent bowler.
If you can visit a coach for some lessons. Your current average compared to your experience shows a lot of potential. Keep it up.
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