make does not work

[Otto Endres]

Hello,
If I try to type "make" in the Terminal, the Output is:

make[1]: *** [Makefile:55: ffmvforce.o] Fehler 1
make[1]: Verzeichnis „/home/otto/Programme/Linuxconsoletools/linuxconsoletools-1.7.1/linuxconsoletools-1.7.1/utils“ wird verlassen
make: *** [Makefile:32: install] Fehler 2
root@otto-PC:/home/otto/Programme/Linuxconsoletools/linuxconsoletools-1.7.1/linuxconsoletools-1.7.1# make SYSTEMD_SUPPORT=1
make -C utils compile
make[1]: Verzeichnis „/home/otto/Programme/Linuxconsoletools/linuxconsoletools-1.7.1/linuxconsoletools-1.7.1/utils“ wird betreten
cc -g -O2 -Wall -Wextra  -c ffmvforce.c -o ffmvforce.o `pkg-config --cflags sdl2`
Package sdl2 was not found in the pkg-config search path.
Perhaps you should add the directory containing `sdl2.pc'
to the PKG_CONFIG_PATH environment variable
No package 'sdl2' found
ffmvforce.c:38:10: fatal error: SDL.h: Datei oder Verzeichnis nicht gefunden
 #include <SDL.h>
          ^~~~~~~

Whats wrong and how to fix it?