Hi Stan!
Sometimes, it's hard for us to help those outside North America, because some of the test kits and chemicals are very different. Can you get a simple OTO/Phenol Red test kit? Color matching tests CAN be tough to interpret but drop-testing is usually more accurate and easier. For example, the FC test goes from red or pink to crystal clear. The Total Alkalinity test goes from green to red. Ben, our site's owner, is very leery of ORP testers. I know little about them but they have to be calibrated frequently.

Your pH is OK, FC and TC don't tell us anything because we don't know what the limit of the normal range is. You can double whatever that range is, probably, by mixing pool water and distilled water half and half and testing the dilute mixture. CYA is very high. I'll bet anything you're using Di-chlor powder and Tri-chlor tablets. Stop. They have elevated your Cyanuric Acid (CYA) to a difficult range. And your Total Alkalinity number seems extremely high to me. Have you been adding a lot of baking soda to it? Do you have a Hardness measure as well? It's usually not relevant to vinyl pools unless extremely high.

At a guess, you have an algae bloom. The solution is not complex. You'll have to raise your chlorine level to a sufficient degree and keep it raised till the algae is dead. If your CYA reading is accurate, that means to an FC level of no less than 25ppm. It will take several days or more. You can use two chlorine sources. The first is our first choice, always: Bleach. Ordinary, unscented, house-hold bleach, the stronger the better. Liquid Chlorine, sold in pool stores here across the pond, is the same thing, only stronger. Here, "ultra" bleach is available in an 8.25% concentration. LC can be 12.5-14%. It's all called "Sodium hypochlorite". Alternatively, if your hardness level is low, the lower the better, you can use Cal-Hypo powder--calcium hypochlorite. Cal-Hypo doesn't add CYA but does add calcium. Again, if you're not getting close to 400ppm (hardness) it's not a problem.

How much? While we figure in US gallons here, the ratios are the same. Here's the rule of thumb for bleach: If the concentration is 8.25%, one liter of bleach will add 8.25ppm of chlorine to 10,000 liters of water. But it will take two liters of 8.25% bleach to add 8.25ppm of FC to 20,000 liters. So you'd need ROUGHLY 8 liters of 8.25% bleach to raise your pool by 8.25ppm. That works for any concentration--5.25% adds 5.25ppm, 14% adds 14ppm.

Not sure I can do the conversion on Cal-hypo so well, but I estimate that 325 grams of 65% Cal-Hypo powder will add 10ppm of chlorine to 79,500 liters of water + 7-8ppm of calcium.

Meanwhile, read our various forums on dealing with algae, and go to our sister site, PoolSolutions.com and read everything you can.

That's just for starters.

Good luck!