Longer time estimated for a production order

Hello SAP experts,

I have a situation where a single part number (sfg) was planned for manufacturing in a routing that comprised several work centers in its structure, but the output of time line was literally the sum of all work centers required capacities in hours to process that order, it was like the batch order had to pass from 1 work center to another without any parallel work between work centers, which ended up in several days needed to manufacture that order... it resulted way too much time estimated for that order. Any idea how this error can be fixed ?

Thank you!

Albert