To ‘get a foot in the door’ ‘To get my/your/… foot in the door’ means to get part of the way in. Think of entering a house, you usually put your whole body in, not just a foot. If you wished to work for a company, although you might desire a high position, you might be pleased to get started at a low position, just like getting your foot in the door. To put your foot in your mouth. (the phrase is not in someone else’s mouth.) it means to make a mistake, saying something inappropriate. Think of putting your foot in the right place, not in the wrong place. Your mouth is not for that!

Get foot in the door 搶先机. Your resume is your foot getting into the door. Putting your foot in the mouth 言出食其尷尬果 Politicians tend to put their foot in their mouth.