Hello Reginaldo
Generally, performance issues are only observed on the order confirmation if there are too many operations or goods movements.
If there are many goods movements, maybe it is better to post them in update mode. Check the setting on OPK4 and note 208477 for more details.
Otherwise, you should run some traces on ST05 and ST12, in order to identify exactly what is causing the performance.
BR
Caetano