Грамматика русского языка. Часть 7. Имя прилагательное. Глава 12. Сравнительная степень. Russian Grammar. Part 7. The Adjective. Unit 12. The Comparative.

lf we say that something is “more interesting” or “less interesting”, we are using the comparative.
In English we can form the comparative by using the words more and less, or if the English adjective is very short, we can add er to the end of the adjective (it is cheaper). Russian uses the words более
(mоre) or менee (less) in front of the long form of the adjective. This is called the compound comparative.

The words более and менee never change (i.e. in their endings) but the long adjective which follows them must agree with the adjective it is describing:
This is a more (less) interesting town.
She lives in a more (less) interesting town.

Some adjectives do not form compound comparatives. They have a long form comparative of their own. Here are the first four:

Long form adjective	Long form comparative
большой big	больший   bigger
маленький small	меньший   lesser, smaller
хороший good	лучший   better
плохой bad	худший   worse

The adjectives for old and young cannot form compound comparatives if you are talking about animate nouns or groups - they have their own long form comparative.

старый   old	старший   older, senior	Моя старшая сестра. My older sister.
молодой   young	младший   younger	Младший класс. The junior class.

You can, however, say это более старое здание (it is an older building). The adjectives for high and low cannot form compound comparatives if you are using them in the sense which means superior and inferior:

высокий   high	высший   superior, higher	высшее образование higher education
низкий   low	низший   inferior, lower	низший балл lower (bottom) mark

You can, however, say это более высокое здание (it is a taller building).

To be continued.