Hello Sir/Madam,
I have read your requirements, you want to update 4 of your apps with latest dependency and target latest android version and make sure apps to work on latest version freely.
So, Yes I am ready to do this job. I have vast experience in android development so it will be easy for me to go through codes of your apps and quickly update what is required.
I can start now and can do this for all 4 apps in 3 days.
Btw, No I can't help with increase downloads of your app. I have expertise only in development.
Let's discuss over chat if you need any more clarification from my side, waiting for your reply.
Thank you,
Hardip