I don't know how to repair this dents on my 2 front teeth. - How can I fix it? (photo)

I think small, non invasive dental bonding can address your primary concern. Done well they should match in color, feel like your tooth and appears as nothing happened

It is difficult to see the exact dimension of the enamel defects in the photo you submitted.  Tip for future: The best way to take a photo with a phone camera is to not use the selfie camera but rather use the outward facing camera and stand in front of a mirror.Small enamel defects can many times be filled in with cosmetic dental bonding.  This resin and newer ceramic filled resin can blend in beautifully.  For larger defects porcelain or ceramic veneers can give a new face to the teeth that is smooth, life like and blend in with neighboring teeth.

It's possible that these pits came from the orthodontic appliance debonding. It's the risk you take with conventional bracket bonding and orthodontic treatment. I'm not blaming the orthodontist; it's just a fact of life. As to your question of how to fix; composite bonding would be the best. An experienced clinician can bond over these areas with no visible transition area using composite. Good luck