aufmachen
to open
To open something that is closed, for example a door, a window, a bottle, or a letter.
Kannst du bitte das Fenster aufmachen? Es ist sehr stickig hier drin.
Can you please open the window? It's very stuffy in here.

to open
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to open
To open something that is closed, for example a door, a window, a bottle, or a letter.
Kannst du bitte das Fenster aufmachen? Es ist sehr stickig hier drin.
Can you please open the window? It's very stuffy in here.

'Aufmachen' (to open) is a separable verb. The prefix 'auf' goes at the end of the main clause. In subordinate clauses, the verb stays together, and in the infinitive with 'zu', 'zu' goes in the middle.
Machst du bitte die Tür auf?
Will you please open the door?
In the meaning of 'öffnen' (to open), 'aufmachen' (to open) is used for everyday things: 'eine Tür aufmachen' (to open a door), 'ein Fenster aufmachen' (to open a window), 'eine Flasche aufmachen' (to open a bottle), 'einen Brief aufmachen' (to open a letter), or 'ein Geschenk aufmachen' (to open a present).
Er machte das Geschenk neugierig auf.
He opened the present curiously.
In connection with shops, restaurants, or practices, 'aufmachen' (to open) means the initial opening. It can be used with an object ('er macht ein Café auf' — he is opening a café) or without one ('ein Café macht auf' — a café is opening).
Nächste Woche macht hier ein neues Restaurant auf.
A new restaurant is opening here next week.
The reflexive form 'sich aufmachen' (to set off) always means 'sich auf den Weg machen' (to set out) or 'losgehen' (to get going). The reflexive pronoun is obligatory here.
Die Wanderer machten sich schon früh am Morgen auf den Weg.
The hikers set off early in the morning.
The idiom 'ein Fass aufmachen' (to make a big fuss) is colloquial and means to make a big deal out of a small thing or to complicate a topic unnecessarily.
Wegen des kleinen Kratzers am Auto brauchst du doch kein Fass aufzumachen!
You really don't need to make such a fuss over the small scratch on the car!
to found / be based on
'gründen' and 'aufmachen' can both be used when a new business begins. 'gründen' sounds more precise when you bring a company, organization, or family into being. It is often about the official or fundamental beginning. 'aufmachen' fits better for a shop, practice, or branch that opens for customers. It sounds more colloquial. The words can be confused because you can both found and open a business. A useful rule: you 'gründet die Firma' (found the company), and you 'macht den Laden für Kunden auf' (open the shop for customers).

Paul macht im Frühling einen kleinen Laden in der Innenstadt auf.
Paul is opening a small shop downtown in the spring.
Nach dem Studium gründet Lena mit zwei Freunden eine kleine Firma.
After university, Lena founds a small company with two friends.