Howto import a makefile project

Hello everybody, my name is robert.
I installed PlatformIO recently (with Atom) and like it very much. It took very little effort to get it running on my linux mint system. I usually work with windows, but i was missing a platform independent solution besides eclipse. So that is a big plus. I ran into some problems with clangd however but that is not the reason for this post.
I was wondering how can i compile a makefile project, to be exact THIS (GitHub - kanflo/opendps: Give your DPS5005 the upgrade it deserves) project. It uses libopencm3 on a stm32f100. I can compile the libopencm3 test project for the discovery without a problem but i can’t find a dscription what to do with foreign projects. I already made a platformio.ini with this in it:
platform = ststm32
board = disco_f100rb
framework = libopencm3
but i get a compile error “No configuration to build this project exists”
Please give me some advice.
Thank you