parts of speech

[MikeNewYork]

What about word "if"? Is is an adverb?

"If" is almost always a conjunction.

Rarely it can be a noun.

Do it now. I don't want to hear any ifs, ands, or buts.

[Humble]

I guess it's a conjunction, but I'm not sure.
As to verbal nouns, I call it those that have a verb in their root: a painting, an opening, an arrangement etc
Rgs

[MikeNewYork]

I guess it's a conjunction, but I'm not sure.
As to verbal nouns, I call it those that have a verb in their root: a painting, an opening, an arrangement etc
Rgs

You're right about "conjunction".

As to "verbal nouns", that's fine as long as your audience understands what you mean.

[Lenka]

To which word class does the word "nevertheless" belong? Is it an adverb?

[MikeNewYork]

To which word class does the word "nevertheless" belong? Is it an adverb?

Yes it is an adverb. It most often functions as a conjunctive adverb, like "however".