I have a digital system project about $4$ bit digital calculator using Logisim application. I have errors in Circuit: ALU. When I connect outputs from Gates to multiplexers, it shows orange wires and says "incompatible widths". First question, what happened to it and how can I fix that problem? And then, I dragged $4$bit Adder from $4$bit Adder circuit and there are $8$ inputs and $4$ outputs in that $4$bit Adder, but there are only four $4-$to$-1$ multiplexers. Second question, how can I deal with that?

Incompatible widths $(13)$