Can’t use some Gears

I got a Giant Boulder 3 Bike stashed on a Storage room for a while and I noticed some dent in the front derailleur. And that’s what causes the fact of gear 3/3 in the front not to engage so I only got 1 and 2. On the back I can’t use 1 and 2 but I got 3-7. But I don’t see any dents there so maybe adjusting the deraileur should fix those.

Couple of Questions.

-Worst case scenario if I can’t fix and lose these gears, how unpractical is it going to be?

-Besides adjusting the back deraileur, what can be done with the front? Can it be repaired or do I need to buy a whole new accessory.

This will help me make a decision whether I should use this bike at all or go and buy a new bike

https://ibb.co/KLrwwmH

by jesuiscaramel