wa'alaikum as'salaam,
Ibn Qudaamah (may Allaah have mercy on him) said: If standing will make a sick person’s sickness worse, then he should pray sitting. The scholars are unanimously agreed that a person who cannot stand may pray sitting. The Prophet (peace and blessings of Allaah be upon him) said to ‘Imraan ibn Husayn: “Pray standing; if you cannot, then sitting; and if you cannot, then lying on your side.”
It was also narrated by al-Bukhaari, Abu Dawood and al-Nasaa’i, who added: “If you cannot, then lying on your back, and Allaah does not burden any soul beyond its scope.”
If he is able to stand but he fears that his sickness will be made worse, or that his recovery may be delayed, or it is too hard for him to stand, then he may pray sitting down. Something similar was said by Maalik and Ishaaq.
https://islamqa.info/en/67934
Whilst siting, you bow forward a bit for ruku and further more for sujood. Tashahud should be the same?
Google praying salah while sitting to see visually how its done.