How to make buy one get one free for opencart 2.3.0.1

Hello, i wonder if you guys could tell me, how to set a buy one get one free scheme for my shop. i dont want to buy a module for me, because i think its to expensive for such a thing, and i already spend a LOT of money for my shop, and i didnt have any money to buy another module. so is there a way to make a buy one get one for free scheme for opencart 2.3.0.1 ? i dont mind getting my hand dirty for code work. i understand coding basics . just guide me how to.

i tried a turn around for this problem. setting the minimal item to be bought to 2 and set a discount for half the price of the product. but then if the user decided to bought 3 items. its a problem. so please help me. any idea, suggestion, tutorial, etc will be much appriciated.

sorry for the bad english

my email: timothyt87@gmail.com

Anyone can Help?

If you want to do this without an extension, you'll need to use the Discount data for a product, and set the price for every possible quantity. For example, if the product was $50, you'd set it like this:

Quantity of 2: $25
Quantity of 3: $33.33 (which is $50 + $0 + $50 divided by 3)
Quantity of 4: $25
Quantity of 5: $30 (which is $50 + $0 + $50 + $0 + $50 divided by 5)
etc.

you have add a text below the slides with discount offers.