Om du trycker på den här knappen, öppnas dörren.

Om means if here. It introduces a condition:

• Om du trycker på den här knappen = If you press this button

In Swedish, om is the normal word for if in conditional sentences like this one.

Because Swedish normally says trycka på en knapp for press a button.

So:

• trycka på en knapp = press a button
• trycka by itself often means push, press, or squeeze physically

For buttons, switches, and similar things, på is very common and usually expected.

Because Swedish uses double definiteness with den här / det här / de här.

So you get:

• den här knappen = this button
• det här huset = this house
• de här böckerna = these books

The noun stays in the definite form:

• knapp = a button
• knappen = the button

So den här knappen is the normal way to say this button.

Yes. Denna knapp also means this button.

The difference is mostly style:

• den här knappen = more common in everyday speech
• denna knapp = more formal, more written

A useful thing to remember:

• den här knappen is correct
• denna knapp is correct
• denna knappen is not correct

This is because of Swedish V2 word order.

In a main clause, the finite verb normally comes in the second position. Here, the whole if-clause takes the first position:

• Om du trycker på den här knappen = position 1

So the main clause must begin with the finite verb:

• öppnas = position 2
• dörren = subject comes after the verb

That is why you get:

• Om du trycker på den här knappen, öppnas dörren.

If you put the main clause first, you can say:

• Dörren öppnas om du trycker på den här knappen.

Both are correct.

Öppnas is the present tense passive form of öppna.

• öppna = to open
• öppnar = opens / is opening
• öppnas = is opened / opens

The -s ending often marks the passive in Swedish.

So:

• Dörren öppnas can mean The door is opened
• In natural English here, it is often translated as The door opens

Swedish uses this -s passive very often in instructions, descriptions, and general statements.

Swedish often uses the present tense where English might use will.

So:

• Om du trycker ... öppnas dörren literally looks like If you press ... the door is opened / opens
• Natural English meaning: If you press this button, the door will open

This is normal in Swedish, especially for:

• general truths
• instructions
• automatic results
• scheduled or expected future events

So the present tense here is completely natural.

Not always. Swedish comma use is often a bit less strict than English in sentences like this.

You can write:

• Om du trycker på den här knappen, öppnas dörren.
• Om du trycker på den här knappen öppnas dörren.

Both are possible. The comma is often used to make the sentence easier to read, especially when the introductory clause is a bit longer.

Not exactly, though they can be similar in some contexts.

• dörren öppnas focuses on the door being opened, often by some action or mechanism
• dörren öppnar sig means the door opens itself or the door opens, and can sound a bit more like the door is acting on its own

In your sentence, because pressing a button causes the result, öppnas is very natural.

It is fairly neutral and natural. It sounds like something you might see:

• in instructions
• on a sign
• in a manual
• in a building or machine interface

In everyday speech, someone might also say something a bit simpler, for example:

• Om du trycker på den här knappen öppnas dörren.
• Trycker du på den här knappen öppnas dörren.
• Om du trycker på den här knappen går dörren upp.

The version you have is standard and correct.