Someone who is a choleh and is in a matzav that they feel extremely sick (high fever, stomach problems, nausea, dizziness, pains, any of the above) and feel it difficult to move around. What should they do in terms of davening (leaving the issue of Tefillin aside from now.) What do they have to say? What is are they machuyiv to say? What can they skip if anything? What are they patur from? Etc…
I’m sure one can imagine a difficult situation like this and realizing that it’s hard to daven. The shailo is what should be done and what is the reason/sources for it.
The Torah was not given to “angels,” but to human beings, and a person should do whatever he can, and no more than that.
Therefore, if one has the strength to say Keriyas Shema, this of course comes first. After this, shemoneh esrei, which can be recited sitting if one does not have the strength to stand. Shemoneh Esrei should not be commence if one has an upset stomach that will not allow davening to be completed before needing the bathroom. Then other parts of davening — all depending on the person’s ability to daven.
Even if one cannot concentrate on one’s prayer, one should still daven if physically possible, as poskim write concerning a chasan: Although he is exempt according to the strict halachah, poskim write that today, we don’t concentrate well in any case, so that he should daven wherever physically possible.
[I recall that Rav Chaim Shmuelevitz was once davening Shemoneh Esrei, and near the beginning he sat down, exclaiming “I have no strength” (it is possible that he finished the whole prayer quickly).]