Welcome to the forum!
Ideally, you should start with a slingshot where your index finger and thumb are not too exposed during the critical learning stage of correct shooting techniques. A fork width of between 5 and 7 cm is probably a better choice to begin with, with numerous options in terms of slingshot designs available to you. The slingshot you purchased has a fork gap that may be a bit narrow to start with (in my opinion), with a higher likelihood of fork hits.
The bottom line is that the slingshot you use fits well into your hand, and that you use flat bands or tubes with relatively light draw weights and smaller ammo (8 to 9 mm) until you reach a certain level of proficiency. There is no point in trying to aim and correctly releasing the pouch with excessively heavy bands or tubes.
A great way to start is to make a board cut slingshot using birch plywood (minimum 18 mm thickness), and learning how to cut your own flat bands: plenty of templates and relevant advice on the subject in the forum pages.
Otherwise, the "Scout" slingshot by "Simpleshot" (USA) should suit your needs:
https://simple-shot.com/slingshots/1a2xxxxx/the-scout-xt-slingshot
Enjoy!
