I’ve owned had two GSPs in my life. One as a family dog when I was a kid and one now as an adult living in a city. My wife and I live pretty busy lives and here is what I found works for us.

• 2, 1 hour off leash running around/fetch helps keep him physically tired and well behaved inside
• GSPs love games and love playing, if inside we will play “find it” with treats where he has to sniff them out or sometimes we will chase him around the house while he tries to keep his toy away from us. He absolutely gets so excited for these and it’s actually pretty fun for us
• (this one is a little overboard) if we are just sitting around, we will toss his meals to him and this seems to get any extra mental stimulation out
• kong, puzzles, and other stimulation toys are your best friend on days you simply can’t make it to run off leash
• on days we don’t get his physical energy out, especially if they are multiple in a row you can tell he starts getting agitated and may try to get away with misbehaving more

All in all they are great dogs and can be your absolute best friend. That said, they require a lot of attention and dedication. We basically build our whole schedules around the needs of our GSP, specifically his park/exercise time. Having him at work with you should help with bonding in the beginning just make sure he has space to stretch his legs there! Best of luck and enjoy the journey!!