@aliarshad26! You are facing problems. You don't need mechanics. You need YOU, and a bit of common sense.
It took me a couple of years to realize that if you your ride to be perfect, then do all its work yourself. It may not be perfect the first couple of times you do it, but it will be, once you get enough experience on your hands. Even if you mess something up, the thought that "YOU" were the cause, will cool you down because, let's admit it, seeing someone else mess up your ride is more furious.
If you think i am just speaking some words, then you need to visit my own CG125 thread, where quite a few of my experiences are shared. What you are facing with your new YBR-G, i was facing with my CG125. And from the past 5-6 months, i have been doing ALL the tune-ups (oil change, tappet adjustment, even carb tunning and mixture settings) myself, and i am telling you, even when i am not quite satisfied with my word, i am happy because i can change the settings however i want, whenever i want. And i have changed my carb's mixture settings like 5 times, in past 3 weeks. (I keep a screw driver in my bag, and wherever i feel that the mixture is not right, i part the bike on the side of the road and set the mixture again.).
From all the things you have mentioned, your bike seems just fine. You are looking for perfection, which you won't find anywhere. So stop wasting time.
Bike starting issue: Do the valves adjustment yourself, and also the mixture settings (without opening up the carb). A LOT of tutorials on YouTube. Incorrect mixture settings and very tight valves are also one of the reasons your bike may not be starting up properly. The worst case scenario might be a bent valve, but that can't happen in a brand new bike, unless you are hammering it way too hard.
Top Speed Issue: If it goes to 95km/h ... your ride is just fine. Screw those idiots who claim to get 130km/h out of their a**. Its technically not even possible, when ALL the other rides in the same 125cc class are unable to achieve that speed. Even a CG125 these days is maxing out at 105km/h, and that bike is like a paper weight infront of your heavier YBRG.
If I were you, i will stop wasting my time with any Mechanics, and take matters in my own hand. Buy the necessary tools, and DO IT YOURSELF.