Undecided questions
A question... 습니다 , 입니다....

Hi
'~습니다' is a just finishing verb ending and
'입니다' is a predicate that meaning 'is ,am ,are" in english.
입니다 = verb stem 이(다)+ verb ending ㅂ니다.

I think that you confuse a finishing verb ending ~습니다 /~ㅂ니다'.
If the last sound of verb stem is vowel or ㄹ, it will combine with ~ㅂ니다.
ex) 바라(다) -바랍니다 , 감사하(다) - 감사합니다, 이(다) - 입니다.

If the last sound is a consonant except ㄹ or 었,겠 (past tense verb ending) ,
it will combine with ~습니다.
ex) 이었(다) - 이었습니다, 먹(다) - 먹습니다, 좋(다) -좋습니다

끝났습니다. 읽느라고 수고하셨습니다.

-ㅂ니다 is attached to syllable in words that have no consonant except for the consonant 'ㄹ' for representing a movement or state, for example, 좋습니다(is/are good), 좋았습니다(was, were good), 기쁩니다(is/am/are glad), 기뻤습니다(was, were glad), 갑니다(go), '갔습니다(went)', 잡니다(sleep), 잤습니다(slept), 학생입니다(is student), 단어입니다(is word).

The above words(좋습니다, 좋았습니다/ 기쁩니다, 기뻤습니다/ 갑니다, 갔습니다 /잡니다, 잤습니다) into which basic form of Korean verb and adjective(좋다, 좋았다/ 기쁘다, 기뻤다/ 가다, 갔다/ 자다, 잤다) are changed have consonants 'ㅂ' at the lower part of word's syllable. We call this form '합쇼체(하십시오체)'.
-습니다 is placed in the 합쇼체 part, attaching after the syllables that were not changed such as '좋-', '좋았-', '기쁘-', '기뻤-', '가-', '갔-','자-', '잤-'.

Likewise, -ㅂ니다 attaches to 학생이다 and 단어이다 that contain noun like '학생(student)', '단어(word)'. And they becomes 학생입니다, 단어입니다. In this regard, 학생입니다 and 단어입니다 are distinct from the words mentioned ahead.