Repairing the concrete so it looks good:

The first thing you need to do after making any necessary repairs, is to remove any vegetation from the edges and the expansion joints, then put foam rods into the expansion joints as to keep them from filling with the resurfacing compounds.

For concrete restoration

Next you have to treat the stains with a type of acid called Muriatic acid. This must be done carefully! You should wear gloves, eye protection, and dilute the acid (usually about a 1 to 4 ratio of 20% acid.) apply the acid with a brush or spray, allow it to sit, then hose it off with plenty of water.

The next step is pretty simple. Clean the surface (starting in the center and working outward) with a high-pressure nozzle for your hose, or a power cleaner, which you can rent. Take a wet/dry vacuum to the cracks in the cement and clean them thoroughly without getting dirt or debris onto the concrete you just cleaned. Now saturate your surface with water, and then brush it off, leaving a moist surface, and no standing water.

Now mix your resurfacing compound with a power drill with a paddle mixer attachment (which is usually recommended.) the next step is simply to level the area with the compound and fill in small cracks, and allow them to set completely, before completing the job. While you’re applying it, you should texture.
 

Be Safe: Be sure your pool has the correct fencing surrounding it. Everyone's pool should have many barriers to ensure children and or animals cannot get into the pool. Besides just a fence, you may consider adding  a safety cover and a pool alarm.