As suggested by prodigyplace I went to the Synaptic and installed SleepyHead.
And it works very well.
Thank you all for your help

I installed libqt5serialport5-dev but it still does not work: ~/sleepyhead-code/build_sleepyhead$ sudo make cd sleepyhead/ && ( test -e Makefile || /usr/lib/qt5/bin/qmake -o Makefile /home/martin/sleepyhead-code/sleepyhead-code/sleepyhead/sleepyhead.pro ) && make -f Makefile Project MESSAGE: Buildin...

Thanks prodigyplace, Unfortunately I am not good at all and at my age it's going a be very hard to start learning (no matter what THEY say, wait till they reach their 80th.. ). Anyway, I deleted everything (using sudo) and tried your suggestion. There is an improvement - no more " Cannot find file: ...

What I did so far I installed : libqt5serialport5 git qt5-qmake qt5-default libqt5webkit5-dev libqt5serialport5- g++ libudev-dev sudo mkdir build_sleepyhead cd build_sleepyhead sudo git clone https://gitlab.com/sleepyhead/sleepyhead-code.git sudo qmake ../sleepyhead-code/SleepyHeadQT.pro Cannot find...

Please direct me to the right site.

Or better, please give me step-by-step instructions, since I am not that Linux savvy.

Thank you very much