火をおこすって英語でなんて言うの？

▪ Make a fire.
To make a fire indicates that you want to pack some wood and light it up to let he fire burn.

▪ Start a fire.
To start a fire can mean the same as the above sentence or it can mean that you want to be naughty and start a fire in the forest.

Example sentences
a. Let make a fire for the barbeque.
b. Lets start a fire in the forest.

make a fire.- To make a fire means the process of collecting wood and the matches and then lighting up the fire. There if someone is making a fire they actually go through the process of starting a fire.
For example: Let us make a fire for the barbaque
start a fire- To start a fire usually does not need a lot any effort.
For example:
The police are still not sure who started the fire in the bushes

Although these could all be used informal speaking as making a fire they mean slightly different things
To say ' To start' a fire it means to light or set the fire alight so you could also say 'to light a fire'
'To build a fire' means that you put the wood/items in a pile ready to light or start it.

Also, to light a fire, to set on fire, to set something aflame, to set something ablaze, to put a match to something such as paper, to set alight.

We "set fire" to things when we "combust dry material" and flames occur as a result!
When out in nature we may not have the convenience of gas or oil with us..
So we will need to find suitable Kindling to set t he fire up ready for use...
In short ..."we set a fire in the camp clearing".... and cooked supper.

If you want to express that you need a fire to build a campfire, you can say:
"Start a fire"
"Make a fire"

When you find yourself in the countryside and there is hopefully some wood nearby, you may gather the necessary tinder and combustible materials in orde to build yourself a heartening camp fire. You may use any of these verbs: light, start, build, make, construct. You may also say:
"Let's get a fire going!"