problems with formula

TexelFred 

Perhaps

=ALS(
   OF(C21="r";C21="x";C21="w";C21="ta";C21="ao";C21="oa");
   0;
   ALS(C21="rec";
      C22;
      ALS(C21="v";
         7,6;
         ALS(
            OF(C21="wf";C21="z";C21="kv";C21="cd";C21="bv");
            8;
            ALS(
               EN((C22-C21)>5;(C22-C21)<=11;C21>0;C21<12);
               C22-C21-0,5;
               ALS(
                  EN((C22-C21)>=6;C21>12;C22>=19);
                  C22-C21-1,5;
                  ALS(
                     EN((C22-C21)>10;C21<12;C22>20);
                     C22-C21-2;C22-C21
                  )
               )
            )
         )
      )
   )
)