I have built a mono black edh deck. Seems good but i am having issues with beating some green/black ramp deck that creates a lot of tokens. I am open for suggestions for this deck so that i can make it preferably beat this green/black deck. Thanks

https://deckbox.org/sets/778563

First off, it'd be helpful if you identified your commander so that we can have a sense of what we're working with.

Secondly, what type(s) of tokens is the opponent using? The reason I ask is because black has a LOT of options for dealing with smaller creatures but often struggles once their toughness climbs above 3 or 4. For the time being, look into Bile Blight, Drown in Sorrow, Illness in the Ranks, Shrivel, and cards of that nature. The important point is that against a token strategy you do NOT want to be trading 1-for-1 removal for their tokens as you will likely fall behind rather quickly.

I am using Erebos, God of the Dead as my commander.
And i will have to look through his deck to see what cards that he is using to create these tokens.

Well, more simply put, are you being beaten down by 1/1s (spirits, soldiers, saprolings, and squirrels) or is it more 3/3s (beasts for the most part)?

Well i have his deck and i have been looking through it, searching out the cards that he uses the most. Avenger of Zendikar is used a lot. So what is happening is he is getting like 16 1/1s at once( using Korozda Guildmage) then they grow from landfall from Avenger of Zendikar. Not to mention the 0/1 green plant creatures that Zendikar makes when comes into battlefield. So i am overwhelmed very fast with these tokens.

Decree of Pain can destroy all creatures, or give them -2/-2 until end of turn.
Extinction destroys all creatures of a type. Bye bye plants! Tsabo's Decree has the same effect, plus a bonus.
Forced March is a great way to get rid of tokens.
You can build up a lot of mana in mono-black, so In Garruk's Wake, Plague Wind and Overwhelming Forces should be usable.
Pestilence effects are a great way to clear a board - try Pestilence, Crypt Rats, Thrashing Wumpus, Pestilence Demon...Toxic Deluge will help as well.

Also, just a note - the tokens from the Guildmage don't grow from Avenger of Zendikar's landfall ability. The Guildmage makes Saprolings, and Avenger of Zendikar only boosts Plant creatures.

Given that you're talking about just 1/1s, you should pick up copies of Illness in the Ranks, Curse of Death's Hold, Bile Blight, Drown in Sorrow, Black Sun's Zenith, and the others mentioned by Deucebot.

Note that things like Illness and Curse would kill even the plant tokens from Avenger as he comes out, his trigger to make the plants goes on the stack, and only once another land is played would that trigger go on the stack. Both Illness and Curse impose state-based effects which check every time anything on the stack resolves - so the plants would enter and die immediately.