Tolong matikan lampu dengan sakelar di dekat pintu.

Tolong makes the sentence sound like a polite request.

• Matikan lampu. = Turn off the light.
  This is a direct command.
• Tolong matikan lampu. = Please turn off the light.

In Indonesian, tolong is very commonly used to soften an instruction. It can be translated as please, but it originally also has the sense of help.

Because mati and matikan are different.

• mati = dead, off, or to die / to be off depending on context
• matikan = turn something off / switch something off

So:

• Lampu mati. = The light is off.
• Matikan lampu. = Turn off the light.

The ending -kan often makes a verb mean cause something to become a certain state.
So matikan literally has the idea of make it off/dead.

Indonesian often leaves out the subject when it is obvious from context, especially in commands and requests.

So:

• Tolong matikan lampu... naturally means Please turn off the light...

There is no need to say you. English usually requires a subject, but Indonesian often does not.

Yes. In this sentence, matikan is functioning as an imperative, meaning a command/request: turn off.

A very common pattern is:

• tolong + verb for polite requests
• verb alone for stronger commands

Compare:

• Matikan lampu! = Turn off the light!
• Tolong matikan lampu. = Please turn off the light.

Mematikan is the active verb form, but after tolong in a request, Indonesian very often uses the bare base form instead:

• Tolong matikan lampu. = the most natural form here

You may also hear:

• Tolong mematikan lampu.

but this is generally less natural in everyday speech for a simple request.

So for learners, it is safest to remember:

• tolong + base verb is very common and natural

Here dengan means with in the sense of using.

So:

• dengan sakelar = with the switch / using the switch

This tells you the method or tool used to do the action.

It is mostly understood as:

• using the switch that is near the door

The phrase di dekat pintu most naturally describes sakelar (switch), not lampu.

So the structure is:

• matikan lampu = turn off the light
• dengan sakelar = with the switch
• di dekat pintu = near the door

Together: Turn off the light using the switch near the door.

Sakelar means switch, especially an electrical switch like a light switch.

It is a correct standard word. In everyday speech, though, people may also say:

• tombol = button
• switch = borrowed from English in casual speech

For a light switch, sakelar is clear and accurate.

Both can be heard, but di dekat pintu is more explicit and standard here.

• dekat = near
• di dekat = at/near, in a location near

Because this phrase describes location, di is very natural.

So:

• sakelar di dekat pintu = the switch near the door

If someone says sakelar dekat pintu, it may still be understood in casual speech, but di dekat pintu sounds more complete.

The order is:

• Tolong = please
• matikan = turn off
• lampu = the light
• dengan sakelar = with the switch
• di dekat pintu = near the door

So Indonesian is following a very natural pattern:

please + verb + object + extra information

This is one reason the sentence feels quite straightforward to English speakers.

Indonesian does not usually use articles like the or a/an.

So:

• lampu can mean a light, the light, or lights, depending on context
• pintu can mean a door or the door

In this sentence, context makes it clear that it means something like:

• the light
• the switch
• the door

This is very normal in Indonesian.

Yes, you could say:

• Tolong matikan lampunya.

The ending -nya often makes the noun sound more definite, like the light or that light.

Compare:

• matikan lampu = turn off the light / a light
• matikan lampunya = turn off the light / that light

Both are possible. The version without -nya is already perfectly natural.

Yes. Tolong matikan lampu dengan sakelar di dekat pintu. is polite and normal.

If you want to be even softer, you could say:

• Tolong, matikan lampu dengan sakelar di dekat pintu, ya.
• Bisa tolong matikan lampu dengan sakelar di dekat pintu?

These sound more conversational. But the original sentence is already polite and appropriate.

Yes. That is one reason learners sometimes get confused.

• Tolong! can mean Help!
• Tolong matikan lampu. means Please turn off the light.

So the meaning depends on how it is used:

• by itself: often Help!
• before a verb: often please / please do ...

Not exactly. A literal breakdown would be something like:

• Tolong = please
• matikan = turn off
• lampu = light
• dengan = with
• sakelar = switch
• di dekat pintu = near the door

But natural English would usually be:

• Please turn off the light using the switch near the door.

So the sentence is fairly close to English in structure, but a fully natural translation still needs a little adjustment.