How to target android sdk version 28 in order to put an app on the play store?

Hello everyone ^^, I tried all day searching everywhere why can’t I put my android app on the play store. This is my first time trying to do so and the program is working perfectly fine on my phone but when I try to put it on the Google play store I get this error :

(I can only put on picture per post so I write multiple post)

Apparently it’s because since the 1st of august they added a new rule saying that the apps must target Api 28 (it was 26 before so the default Api proposed by processing Android mode).
So I need to put “android target sdk” to 28, the problem is that when I do so in the manifest file

it changes automatically at the moment of the exportation…

I tried changing other files like preferences but again it just changes automatically !

Even the build.gradle file wich I changed things like the error of having “28.0.3” which doesn’t work didn’t helped me :

I think that the problem is from the default version of the android sdk built tools which is too old (version 26.0.2) to allow to target version 28 Api but I don’t know how to change that because there are no other updates available :

I tried downloading a more recent sdk build

but I have no idea what to do with it and where to put it so that processing uses this in order to make my app target Android Api 28.

I would greatly appreciate any help I’m getting lost with all those files that just automatically change themselves xD