data  = {5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 
        80, 85, 90, 95, 100}

obj[r_, 
        K_] := (sol = 
          NDSolve[{y'[t] == r*y[t] (1 - y[t]/K), 
              y[0] == 5}, y[t], {t, 0, 10}];   values = 
          Table[y[t] /. First[sol], {t, 0, 10,  .5}];    val = 0; 
        For[i = 1, 
          i < 21, i++, {val = 
                val + (values[[i]] - data[[i]])^2};];  
        val)

FindMinimum[obj[s, L], {s, 0.8}, {L, 75}]

obj[0.75, 30]

Plot3D[obj[r, K], {r, 0.65, 0.85},  {K, 40, 60}]