which of these three words is more suitable if I want to underline, to stress that the specialists will help to protect the clients' websites from hackers and other attacks?
"we will increase your website protection"
"we will enhance your website protection"
"we will improve your website protection"
Yet, one more thing:) I can't find the right word to change "protection", as I have already used it many times and want to avoid repetition. For example, "we will increase your website resistance (?) to external attacks". Is it ok or I need some special word?
They are all acceptable, and can mean slightly different things. An online dictionary and/or thesaurus would help.
On the second point, what about 'security'; 'reduce your website's vulnerability to attack' is another possibility. Reference to 'malware' is a popular ploy among web security vendors, so you could add 'by all known malware threats' (and you could list them). Just don't say 'viri.