1.they will have to wait until I am feeling better.
2.they will have to wait until I feel better.
please tell me which one sentence is correct and if both when should we use them/what is the difference?
3.why is there know the article before :part?
e.g. part of interview?
4.a small attendance/small attendance?
doesn’t attendance as an accountable noun need ‘a’ before?
#1 and #2 are both possible, and there is no significant difference in meaning.
More context is needed for #3 and #4. “part of interview” would normally require an article (or other determiner) for “interview” (for example, “part of the interview”). Another article may or may not be used before “part”, depending on context. “small attendance” normally would require an article (or other determiner), but it is not impossible for “attendance” to be used uncountably. Articles may also be omitted in certain special situations (e.g. headlines, bullet points, notes, labels etc.).