Hi,
Welcome to the RStudio community!
If you like to create this whole expression manually you could simply divide the weights by the variables that have negative impact.
Competetiveness = W1 x Pos1 + W2 x Pos2 + W3 / Neg1 + ...
Another way is to make the weights negative for these variables
Competetiveness = W1 x Pos1 + W2 x Pos2 - W3 x Neg1 + ...
In both cases, the larger the negative variables, the lower the competitiveness. Note that the first expression can only be positive, whilst the second one could be negative depending on the values of the weights and indicators.
If you were doing the opposite and trying to learn the weights (instead of setting them yourself), you'd be doing a linear regression, which has the same type of formula.
Hope this helps,
PJ