The living condition is terrible as the apartment is poorly maintained by tenant and poorly managed by landlord [seller].

Do managers that advertise 8% only do 8% when there's a bundle of doors to manage?

I am a broker and property manager here in Clarksville, TN.

Either myself or project manager wen I don't have time, because most contractors need daily supervision.

The biggest lesson learned was managing stress.

It also includes managing your existing investment well to ensure you aren't bleeding money due to bad tenants, excess maintenance, etc. 

We set up our CPA, LLC, website, marketing plat forms (social media), investor (sponsors) list, I have an operation manager, acquisition manager, and myself leading the charge.

In order to do this you need to have deal flow and you need to know 1) How to recognize a good, profitable deal, 2) How to put together funds quickly to buy the deal before someone else does and in such a way where you are protected and the deal is protected, 3) How to run the project so that you follow the budget and don't overspend or overbuild, 4) How to attract an end buyer or a renter and which documents to use to protect yourself and the buyer, 5) If you are going to keep the property then you need to know how to set up the property from the start to best help you in the refinance later, and 6) You need to know how you are planning on managing the property from the beginning in order to make sure it will be profitable at the end.

It sounds like you may not be cut out to manage rentals in which case you should probably sell.

You can manage your risk.