Identification on this leather armchair  

These can look great again either you do the work by yourself (like most here at DA forum) or if you have the means, have all the work done by professionals, but you also have to consider from where you are if the cost to do the repairs by yourself or to pay someone to fix them is worthwhile than just finding vintage examples of the stuff you like in good to better condition that does not need any repairs.
Clean them up first and then assess how you want to proceed with these which part of the chairs need immediate attention to make them useful and presentable again.
This applies to your 2-seater post too.