Black water pours out of the heater system into intex spa

E 97 is an error code that indicates a dry fire protection system has been activated in your Intex Pure SPA. This means that the spa has sensed that there is not enough water in the system, and it has automatically shut down the heater to prevent damage.
To solve this problem, you will need to add more water to the spa. Once the water level is above the minimum level required for safe operation, the dry fire protection system should reset itself automatically.
It is not recommended to run the filtration and the bubbles or jets without enough water in the system as it can cause damage to the pump and other components. Therefore, make sure to add enough water before turning on any functions of the spa.
Also, make sure to check for any other causes that may have led to the water level dropping too low, such as a leak or drainage issue. If you continue to experience issues, refer to the owner's manual or contact Intex customer support for further assistance.

This could be several things. It could be the water flow is too low to keep the heater from overheating, it could be the pump is cavitating and resulting in too much air before the sensor. The sensor could be bad etc. You are essentially correct though

The E90 code on the Intex spa is due to a dirty water flow sensor. ... The black wire is plugged into a white wire, carefully unplug it and unscrew the sensor. Clean it good and blow out the hole it goes in. This will fix the code and you will be back in business https://www.justanswer.com/pool-and-spa/ap9qh-i-m-having-error-code-90-intex-hot-tub-intex.html

by some shock it from Walmart and keep chlorine in it

It looks it would be worth fixing, first I would check the power, the plugs and voltage. it has heat so it requires the proper power cords to supply it,
If all checks out I would contact intex, if there is not any warranty, I would search your area for a electric motor repair shop, tell them its a spa pump with a heater,
I would be happy to look at it for you at no charge to see whats it's fault is. I'm in central Florida.. here are the error CODES. best of luck.. Jay

Intex E96 code means there is a heater fuse error , replace the fuse & your problems should be fixed

well first the manual should say what a error 96 is but i'll save you the trouble , the control is saying heater failure as the water should never be 143 degrees this would burn/kill you if you got in , id look at temperature probe 1st (its in pipe right past the heater ) and next id look at control itself , sometimes water intrusion dammage in controller makes for some "funny" and wrong things to happen

Remove the salt cell housing and plug one end. Pour cell cleaning solution into the housing until the cell is covered. The cell is clean when no further bubbles are formed and you can see shiny metal cell plates.
Remove the cleaning solution flush the cell with clean water and install the salt cell housing back into the system.

You need a sequestering agent to get the metal out. Get a quart at your professional pool supply house and follow the container instructions.

For best results, chlorine should be at minimum or at zero.

Before you do this ... does your pool have a heater attached? What is the pH? If there is a heater and the pH is below 7.0, the water could be eating the copper jacket in the heater. Make the pH right before you do anything. pH should be at 7.2

Thanks for your question @ FixYa.com

Both of your questions depend on one important issue.
What is the BTU's of your heater. The more BTU's the quicker it will heat and also keep it to a specific temp easier