Welcome.
You are not doing anything wrong. Live view is a special mode and not ideal for everyday shooting for those who enjoy a DSLR camera. When you take shots in viewfinder mode, the mirror raises and the shutter opens and closes after the shutter time. Nice and quick, normal SLR camera behavior. In live view the the mirror is up and the shutter is open to expose the sensor full time for live view. You snap a picture and the shutter closes. Then it opens for the selected shutter time, then closes to end the shutter time. Then the shutter opens to return to live view. Lots of clicking and if you check the shutter count, you will see two counts are used for a live view snap. It's never going to be as quick as viewfinder mode because of all the mechanical stuff going on.