vishalwin wrote:can we use BUT ALSO without NOT ONLY?

Yes.
While not only must be followed by but also, but also does NOT have to preceded by not only.
For an official example, check my post here:
https://www.beatthegmat.com/not-only-did ... 84977.html

That sentence works.

Look at what it is saying. Basically it says that Pinto's income is soaring, but his expenses are also soaring. There are two contrasting ideas connected by but.

Not only ... but also is used to convey a particular thing, that not only is one thing the case, but also something else is the case.

One can use but also on its own if one wants to convey something different from what is conveyed when the two are used in combination.

We have to remember that money is not everything, but also we have to remember that in today's society money is the currency used by most people.

When not only and but also are used together, they indicate that two things are the case. When but also is used alone, it may convey that the second idea being discussed contrasts with the first.

Notice that you could break up that last example sentence into two sentences. So the but is being used as a connector, a contrasting conjunction, and the also is part of the second thought. So technically we have not exactly used but also, but rather first but, then also.