For my personal assistant...

 I would choose Leonardo Da Vinci to be my personal assistant for a week because I love art. I'd have him paint me, I'd want like 600 different paintings of me. Like maybe one of those giant paintings that rich people get with their head on some buff person's body as they ride a tiger into battle. I'd want paintings of other things too though. I'd watch him work to see how he does things. I'd ask him about his inspirations and have him teach me all of his techniques and how he draws. I just really like art so I decided to choose the most artistic person on the list. I think it would just be pretty cool to hang out with an artist that people consider to be one of the greatest. Plus free portraits, heck yeah. I want him to paint my dog but like as a majestic lion.

On a magical smartphone...

A standard app that should come with a magical smartphone would be a holographic clothes changer. You would wear a simple outfit underneath but you'd choose an outfit from the selection on your phone and it'd magically project it so it'd look like that's what you're actually wearing. It'd stay on till you change it and no one would know that it was holographic. The clothes would look and feel like actual clothes. You'd have the option to buy more closets with a lot more clothes too. You could also just talk to you phone to tell it to save your outfit in a certain folder. Like, if you put together an outfit and you look in the mirror and say, "dang, I look smokin'," then you can just tell your phone to save it into your favorites folder. Or maybe you've got a hot date or whatever and you have a couple outfits saved in your folder named "ayy bb gurl u lookin fine."

yeah

 Rather than a restaurant, I'd want to open a cafe. The cafe would be sort of small and hidden with big bushes and flowers outside the windows. The whole entire wall that is opposite from the main counter and facing the outside street would be windows. People could enjoy their visit whilst still having the opportunity to still look at the outdoors. There would be a small, more private, corner in the back if people would not like to be towards the windows. You would also have the choice of sitting at the bar counter. The menu would contain all sorts of coffees, cappuccinos, espressos, etc. It'd also have little desserts like brownies, cakes, cookies, muffins, and donuts. It'd probably also have little sandwiches available. I'd like to think it'd be like a reading cafe, so you could sit down and read a book for a while and have coffee too.