Welcome to motorcycling.
You will likely get a fair bit of advice from most of the grey-beards here...listen to that.
But we all secretly envy you since we all remember what this felt like when we were doing it a few (or more) decades ago.
So here is some advice:
For yourself.....swallow some of that youthful pride and find at least two training courses.
One for street/road riding
The other for trail,dirt and off-road riding.
These two courses will pay for themselves very quickly since they will allow you to learn in a few days what would normally take a few months of falling off and bending stuff to learn if you do it the "hard way".
You might also consider finding a local riding club that does off-road riding, joining with others with more experience will save you time and money.
For the bike:
If there are no crashbars fitted. Get some and put them on.
Install "barkbusters" or some form of handlbar/lever protection.
There is not "if" about falling off....just "when". If you are just starting to ride off-road, you will fall. The crashbars will pay for themselves in saving the Transalp's expensive plastic and the bar-ends will save bent and broken levers and allow you to pick the bike up and continue riding rather than pushing it home with a broken clutch lever.
On the mechanical side:
Look for cracked and leaking fuel lines first.
If the fuel lines are OK...make certain the "choke" cable is not sticking and that the two choke plungers are moving freely in the carburators.
Be CAREFUL when removing the choke plungers from the carbs. The plack plastic hex nuts are SOFT and easily rounded off if you are not careful. They are also placed in an area that is difficult got get a wrench into.
Keep us posted on how you're doing