15:39a

After Jesus had dismissed the crowds: In this context, the Greek word that the Berean Standard Bible translates as dismissed refers to telling the crowd go home. After the people ate as much as they wanted, Jesus told them to return to their homes. Your translation should not imply that Jesus was being rude or hostile toward the people.

Here are some other ways to translate this clause:

After he dismissed the crowd
-or-
Then Jesus sent the people ⌊home⌋
-or-
Then Jesus told the crowd of people to go home

This same word occurs in 15:32d.

15:39b

He got into the boat: The disciples probably got into the boat with Jesus. But they are not mentioned because Jesus is in focus here. In some languages, it may be necessary to make the disciples explicit. For example:

he got into the boat ⌊together with the disciples⌋
-or-
he ⌊and his disciples⌋ entered into a boat

the boat: The phrase the boat would normally refer to a boat that had previously been mentioned. This boat may be the same boat as in 14:33a. Or, it is possible that the boat belonged to one of the disciples.

Since no boat is mentioned in the immediate context, it is possible to simply say:

a boat (Good News Translation)

and went to the region of Magadan: The word Magadan probably refers to a small village. This clause indicates that Jesus entered the area that belonged to the people of Magadan.

Here are some other ways to translate this clause:

went to the area of Magadan (New Century Version)
-or-
came to shore near the town of Magadan (Contemporary English Version)

-or-

arrived at the land of ⌊the people of⌋ ⌊the town of⌋ Magadan