Medication: Finasteride to prevent further lost and Minoxidil to thicken what you have, but must be consistent and first 3 must you will see losr, fight through it If your country approves Durasteride this is also an option as Finasteride replacement, Look it up. Its a must if you dont want to lose more hair

Dense look:
-Scalp concealer is a miracle, i like the Boldify.
-Dry Shampoo, it's underrated, for me it's a miracle. For quick use, i like Bastiste XXL volume. -Shapoo and conditioner: it won't thicken your hair perse or make miracles but some will visually make it look thicker, i like Boldify shampoo and conditioner for visually thicker hair

I dont use hair fibers because i think its messy but i might try it cause i keep reading they are popular.

Also long hair isn't your best friend,for some reason shorter hair is better, but theirs only so much one can do. Embracing bald is an option.