Исправь ошибки 1. There is a armchair in the living room/

1). There is an armchair in the living room.

The indefinite article an is needed, because the following word armchair starts from the vowel.

The armchair is rather comfortable. No mistakes.

2). There are two sofas in the house.

The definite article the is needed, because the furniture is in the particular house.

The sofas are little. - No mistakes.

3). There is a car in front of the house.

The indefinite article a is needed after the introductory structure there is.  

4). There is fish and chips are for lunch today.

It is necessary to use there is structure to say what is cooked for lunch.

5). It is cold today.

It is is used to speak about the weather.