I need help coding my buy and sell positions and closing them, and lot size to

Hi guys,
So I'm a resident doctor who's gotten hooked on trading, 2years so far and dare I say it's profitable.
So cus of my schedule I decided to learn how to code my own EA.

Here goes..
My plans quite simple, basically 5 and 10 MA cross-over.
I've successfully defined all my parameters and how it should go.
But the problem I keep getting errors in is opening and closing buy and sell orders and lot sizes.
What I want is simply to buy when 5 crosses above 10,then close when 5 crosses below 10 and open a sell order immediately, just 1 order at a time.
And for the lot sizes, I want it to automatically calculate my lot size to always take one fifth of my free margin so I wouldn't get stuck on a fixed lot size as my balance grows.

I'd really appreciate whomever can guide me through this process.. Thanks in anticipation, all ideas are welcome.

MT4
Use at your own risk.
Please, try it on demo acc first.

Even if you have half-baked knowledge of programming you should be able to create an algorithm for yourself using python for MT4. It’s fairly easy to use. I thought of myself as technologically-challenged before I created 2 EAs for daytrading stocks and forex on charles schwab and fxview. Although I use RSI for trend trading and manually sit in front of my system but at times I make use of eas to trade and send me alerts. To be honest if I could do it anybody can :)