have a low mushy pedal

It sounds like you either still have air in the line or you have a defective master cylinder. I would go around to all of the bleeder screws and make sure you have all the air out. Have someone pump the brake pedal about 5 times, hold the brake pedal, then crack the bleeder open on the caliper, close the bleeder screw, and repeat process until you have a steady stream coming out. Usually 3-5 times per caliper. If this doesn't work, you may have a bad seal inside the master cylinder preventing the pressure to build up and be pushed down the brake lines. Here is a video and guide below to help you bleed the brake system correctly.

https://youtu.be/w7gUsj2us0U

and

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

and

https://youtu.be/WDxvEQrMkBg

Please run down these guides and report back.

Thank you I will replace the master cylinder. The other bleeding steps have been performed.

If I replace the master cylinder. How do I bleed the brakes with ABS.

No problem. The process doesn't change for bleeding the brakes due to ABS. The fluid should still be forced through the ABS module, into the brake lines, to the brake calipers.