grammar - How to form a noun of a verb in the English language

The -ing form of a verb known as a gerund does behave very much like a noun; it usually has the sense 'the act / process of'.

Painting can be very pleasant.

Understanding came gradually.

But the present participle is also formed by 'adding -ing' to the base form of a verb:

I was painting the fence.

And true (deverbal) nouns may have arisen in the same way:

You've burnt my painting/s.

Not to mention (participial) adjectives:

There was a sickening crunch.

While nouns can have many forms (compare these with the corresponding forms of the verb): gain, house, worker, sailor, beggar, devotee, belief, composure, contentment, leakage, admonition, collision, dogmatism, forgery, conspiracy, protectorate, ignorance, vacancy ...

There are nouns (not including gerunds) corresponding to verbs in many cases; they usually have different meanings from the gerunds.