If you have a grammar question, this website probably isnt the best place to find the answer. There are many dedicated grammar sites, so all you need to do is put your problem into a search engine (e.g. Google).
A student asked me to explain how to use "not only... but also...". If we do a Google search for "grammar not only but also", heres the first website that Google suggests: click here.
After reading the explanation of "not only... but also...", you could try making your own sentences about common IELTS topics, such as education, work or the environment.