having mpb & effect of bad cream on my scalp

[worried]

hello
my age is 28, i started my hair loss at the age of 21. It effected me very much i loose my confidence when i meet with girls. i always feel that i am not looking good.
I think i have a severe mpb . hair line is still good,temples are not bad but crown and top of the head is emptied and my scalp is clearly visible.
Now i want to save as much hair i can (without taking finasteride) so that in future i can do a hair transplant, plz advice

what age is best for hair transplantation ?

Any herbal remedy would be very helpful
Does mpb stops after some years or it continues forever ?

My another fear is at the age of 25 I applied a wella cream (hair straightner cream) after shampoo from that i had a very severe burning sensation on my scalp it was so painful that my tears flown out but after washing my head with water it was gone after some hours, Now i fear that if that incident damaged my scalp would i be able to do a hair transplantation ?

thank you

Sorry about my english it is not my native lang.