GETH Private chain, Contract making and API making

I'm a game developer.
I want an Ethereum API that will be used in my game backend engine.

e.g )

- * - * - * -- * - * - * -- * - * - * -- * - * - * -- * - * - * -- * - * - * -- * - * - * -- * - * - * -- * - * - * -- * - * - * -- * - * - * -- * - * - * -

=========================
before
=========================
A user ( have $ 10,000 )
B user ( have $ 20,000 )
=========================

( Action )
A user -> send $ 1,000 -> B user


=========================
After
=========================
A user ( have $ 9,000 )
B user ( have $ 21,000 )
=========================

This process can be implemented in the game as follows.


type 1)

send_money @my_session, @target_session, 1000;

type 2)

if(get_money(@my_session) > 1000)
{
del_money @my_session, get_money(@my_session) - 1000;
set @check, 1;
}
else
{
message @my_session, "you don't have enough money !! ";
set @check, 0;
}

if(@check == 1)
{
add_money @target_session, get_money(@target_session) + 1000;
set @check, 2;
}

if(@check == 2)
{
return;
}
- * - * - * -- * - * - * -- * - * - * -- * - * - * -- * - * - * -- * - * - * -- * - * - * -- * - * - * -- * - * - * -- * - * - * -- * - * - * -- * - * - * -

If you look at the flow of the code above, you can observe the process of sending and receiving money or deleting it.

Therefore,

1) create a private chain with Ethereum-based GETH,
2) repurposed to public,
3) Write an ERC-20 token contract with the features described above
4) Write it as an API that can be used in a C language-based server.

my job - 5) Change the above function(game server) to a contract function(ERC-20 function) using the api you wrote.


6) Check whether it works normally.


I'm waiting for the help of someone who understands and can carry out the series of processes.


thank you.