Is my bike any good?
Is my bike any good?


It depends on what you mean by "good".

There are many definitions of the word "good". Definition 2.3 and 2.4 in the dictionary are a good fit for this situation.

Good
Lexico


  2.3 Useful, advantageous, or beneficial in effect.
  ‘a little sun is good for you’
  
  2.4 Appropriate to a particular purpose.
  ‘this is a good month for planting seeds’


If your bike is useful to you and appropriate to your purpose then yes, your bike is good.


  I wanna use it for proper mt biking but I wanna know if it will hold up or if I should sell it and get a new one. thanks :)


We can't know how hard you will be on your bike and there is no data on how much abuse your bike was designed to take. How you ride is a key factor in how long a bike will last no matter how rugged your bike is.
In the absence of critical information we cannot make a determination on how well your bike will hold up. 

My recommendation is that you ride what you have.


Time in the saddle will tell you what kind of riding you like. This information will be useful when or if you move to another bike.
As you ride things will break. This will tell you what features to look for when or if you move to another bike. For example - suppose you are unhappy with the braking capability of your bike. You can look into modifying your current brakes (better brake pads for example) or make sure that better brakes are on the list for your next bike.
Selling your current bike won't offset the cost of a better bike by much.


Everyone has to start somewhere. What's important is that you get out there and ride and keep on riding. Only you can determine what meets your needs and is "good".