I just booked a ticket with a stop in Beijing. On my way back I will arrive in Beijing at 11:30 (Sunday), but my flight to UK is scheduled at 1:30 (Monday), more or less 14 hours. So I was thinking doing a little bit of tourism and maybe shopping (Maybe some gadgets). But I don't know if I'm going to find all the stores closed or something like that. In that case, what else can I visit during the day? I can imagine there will be no many people who can understand english, so I don't really know what are my options.
When I was in Beijing in 2012 Sunday was not really a big deal. Maybe some shops open a little later, but generally they're all open.
However, as you only have limited time there I would advice to go to see the city instead of buying gadgets which are the same all over the world.
Here are some things in Beijing you could see in this short amount of time:
These are just some options you could choose in Beijing. The visit times are a rough indication on how many time you will spend there. I think that in one day you can visit one or two places listed above.
As you will arrive at 11:30 at Beijing Capital International Airport, you'll probably be in the city around 13:30. There's a subway going from the airport to Dongzhimen from where you can easily take other subways into the city. Buy a subway card at the airport and load it with some money. Taxis are mostly slower in the city because of the traffic jams.