Hello everyone- Help me out please!

Well hello world ..... I currently have a Lexmoto XTRS 125. I would prefer a dirt bike style road legal but they seem more pricey. Anyway I am hoping to make the best of what I have. Any ideas on what I can do the pick up its pace.it can do almost 75 downhill but I am certain it can do much better. I will putting a big bore kit on it to make it 180cc but anything else anyone can recommend would be appreciated.
Its currently all stock parts apart from clutch cable and tires. Tires will be changed again though the current ones are cheapies thrown on after a puncture.
Also my gears seem to be very very stiff to change the lever is fine but the actual gear change is quite tricky. I also cannot get it into neutral while the engine is running.
When upgrading an exhaust do I need to change the downpipe??

Total mech noob at your mercy guys lol