How can I get the best deal on a mortgage?

Can you recommend any lenders .... Where? UK? Nigeria? Pakistan?

'good' also means different things to different people.

I suggest you talk to a mortgage broker, ie one that can arrange a mortgage from a variety of lenders to find the one that suits you. If you just go to your bank, they can only offer you their mortgage, which might not be the most competitive.

Only do fixed rates and the higher your credit score the lower your interest rate will be. You assume a mortgage based on your credit score. I highly recommend going through a credit union to get them do your mortgage. I don't recommend Wells Fargo or bank of america, just my personal opinion. I'm not saying they're bad banks 

My advice is to go with a smaller lender, not one of the huge banks.  To the huge banks you are just a number in the computer and they really don't care if you get the mortgage or not and won't make any attempt to help you through the process. To a smaller or even regional bank, maybe one where you bank at, at least there is usually someone you can talk to who might advocate for you a bit.  Beyond that, I'd try a mortgage broker if you are having trouble getting the loan at the lender, but otherwise try using someone you know and do business with but again, I'd stay away from the huge banks if you could.

Mortgage rates have to be competitive because they are so easy to view publicly.

There is no "one" great rate. 

- It's financial deal, you pay points you get a better interest rate.  But in 2020 with such low rates, I don't think paying points for anyone would make sense.  Normally, an ARM would get good for a flipper but even that is not a great deal right now.

- For me: I'd never pay an application fee.  But I have an over 800 FICO score and the only debt is a car & house, thus I can choose to be picky since everyone wants my business.  For you, how close are you in terms of being able to qualify.