Which word is more appropriate?

i think you can use word "wholly" or for example "fully"

It is natural informally. In more formal language you could perhaps substitute "completely", or simply omit "totally".

"I am always open to any suggestion." (An adverb of time is better than an adverb of degree.)

If you want something less hackneyed:
"I respectfully and thoughtfully consider all suggestions, especially if they are constructive criticisms.

AlpheccaStars"I am always open to any suggestion." (An adverb of time is better than an adverb of degree.)

For me, "always" changes the meaning. It suggests some kind of open-ended commitment, or constant availability, which the other choices do not.

GPY It suggests some kind of open-ended commitment, or constant availability, which the other choices do not.

Right. The "always" would apply to a CV or motivation letter; whereas the sentence without it applies to a current problem or issue under discussion. The addition of "totally" adds a tone of slight frustration, as if all prior suggestions had

AlpheccaStars The addition of "totally" adds a tone of slight frustration,

I don't really perceive that.

Thank you all for your contribution. I think a little clarification is helpful here:

Actually, there is a proposal for doing something by me. However, I'd like to show that I am also open to any other suggestion about that matter. Therefore, I think using the word "always" does not suit here; because in this case I'm not talking generally. In fact, I'm just open to suggestions for this sp

I agree that 'totally is inappropriate, and that there is no need for any modifier at all.

Unlike GPY, I think that 'always' is possible here. In this particular context I think 'always' does not necessarily carry the general-time idea.