Unfortunately , I can't really offer or recommend a riding partner , as I am not near your area ........ But ....... What I would suggest , is continue riding with the "better" riders and to watch what they do and when and how they ride a certain area or obstacle , as you will learn the lines they use , and how they tackle obstacles by observing how they do it , as riding with people with knowledge is the best way to gain knowledge .... it will give you more confidence , because you will know , if they can do it , then you can do it ..... maybe not as well at first , but the more you try , the better you will become as a rider ....... Obviously do not try things you know are way above your ability/skill level , but I am assuming , the people you are riding with , would not purposely put you in a situation where it would be unsafe for you to follow (hopefully they are watchful of others , and observe the fact that not everyone is at their level of experience when tackling terrain)
Just keep riding and you will get better , don't let the better riders intimidate you , use their skill as a learning tool by paying attention to what they do , and you will be surprised at how fast you pick up on things , pay attention to how much throttle they use , and when and where to use the front and/or rear brake , as different situations call for different braking and throttle methods , due to the smaller size of your current bike , it will maybe take more effort to do the same thing , or you may have to go about it differently , just use what you watched them do as a guide , not as a matter of you have to do it exactly as they do .. .... Above all , have fun , if you are too worried about failing , you will miss out on all the fun riding gives ..... be patient , I have been riding since I was 5 and I still learn new things about riding every time I go , and I ride almost every single weekend , and I will be 60 in a month . So you are never too old to learn , and you never stop learning ....... remember that , and you will be fine

........ , do not put yourself down or limit yourself by what you have not accomplished , you are just starting out , pride yourself in the fact that you are accomplishing something each time you ride ... THAT is what is important , is that you try , not if you succeed or kept up with everyone ... They were beginners too .... just take your time , and it will all become natural to you at the pace you are comfortable with ...
