How does a sick person purify himself and pray? I hope for a detailed explanation of that.

The sick person purifies themselves with water. If unable, they perform tayammum. They may perform tayammum on any pure surface that has dust. Tayammum is invalidated by whatever invalidates ablution (wudu) and by the ability to use water. If the sick person cannot purify themselves, another person purifies them. Whoever has a wound or illness that is harmed by water performs tayammum and washes the healthy parts of their body. Whoever has a wound on one of the limbs of purification should wash it; if that is harmful, they should wipe over it; if that is harmful, they should perform tayammum. The person with a splint (or cast) wipes over it.

It is obligatory for the sick person to purify their body, clothes, and place. If unable, they pray in their current state. A person afflicted with urinary incontinence performs ablution and cleanses themselves (istinja) for each prayer after its time has begun, and they wash whatever has been soiled, or they designate a clean garment for prayer.

It is obligatory for the sick person to pray standing. If unable, then sitting. If unable, then on their side. If unable, then lying down. Whoever is able to stand but unable to bow (ruku) and prostrate (sujud) prays standing and gestures for them. Whoever is unable to bow and prostrate gestures for them, making the prostration lower than the bowing. Whoever is unable to prostrate alone should bow and then gesture for prostration. Whoever cannot bend their back should bend their neck. If they cannot gesture with their head, they should say takbir, recite, and intend with their heart. Whenever the sick person becomes able to do what they were previously unable to do, they build upon their prayer. Whoever sleeps through or forgets a prayer should pray it upon waking or remembering. It is not permissible to abandon prayer under any circumstances. If it is difficult for the sick person to perform each prayer at its designated time, they may combine the Dhuhr and Asr prayers, and the Maghrib and Isha prayers.