Val's corrections above are all correct; mine are just another perspective.

I want to help tourists in Moscow.

I am a volunteer who should helps foreigners in Moscow. Please check the next following sentences:
-You can get there on foot, it’s not far. it will take you about 20 minutes. But you can also get there by subway or bus.
-A metro ticket costs 40 rubles. A bus ticket costs 100 rubles, but you can used the ticket 4 times.
-Do you have tickets? You can buy tickets in a gloss the glass building. {Can you see the building from where you are?  If not, be prepared to give directions.}
-I have google translator if you need it.
-I will try to help you. {Correct, but more common is "I can try to help you."}
-I hope I helped you.  {Again, not wrong, but more common is "I hope this was helpful."}
-I am looking for information on the internet.
-The visiting museum Visiting the museum costs two hundred and fifty.
-We can accompany you if you need it help (or "if you need assistance" or "if you need us to").
-Do you have free time.
-Do you have a minute. {Better than "Do you have free time" unless you're talking about *a lot* of free time}
-Can you help us? We have to take a photo with tourists for our report.
-Can you take a photo with us.
Thank you :)

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Nicely done!  Good luck.

I want to help tourist in Moscow.

I am a volunteer who is helping (?) foreigners in Moscow. Please check the following sentences:
-You can get there on foot, it’s not far. It will take you about 20 minutes. But you can also get there by subway or bus.
-A metro ticket costs 40 rubles. A bus ticket costs 100 rubles, but you can used the ticket 4 times.
-Do you have tickets? You can buy tickets in the glass building.
-I have google translator if you need.
-I will try to help you.
-I hope I helped you.
-I am looking for information on the internet.
-The visiting museum costs two hundred and fifty.
-We can accompany you if you need (help). ("it" is not necessary and it refers to a specific thing. You        could say rather help) 
-Do you have free time? 
-Do you have a minute? 
-Can you help us? We have to take a photo with tourists for the report.
-Can you take a photo of/with us.
Thank you :)