I reallt does not understand how to use xmodmap. Can someone please explain it to me? I have scanned the manual pages and seen some examples, but that did not help much....

The characthers I miss the most are:
- = - (hypen)
Alt Gr + - = – (en dash)
Alt Gr + Shirt + - = — (em dash)
Alt Gr + . = … (horizontal ellipsis)
Alt Gr + Å = █ (full block)

I also need a way (preferably something like Alt Gr + f and i) to type:
ct (ligature ‘ct’ - made up by U+63 U+200D U+74)
ff (ligature ‘ff’)
fi (liagure ‘fi’)
fj (ligature ‘fj’)
ffi (ligature ‘ffi’)
ffl (ligature ‘ffl’)
fl (ligature ‘fl’)
ij (ligature ‘ij’)
st (ligature ‘st’)