I used to teach English at school using the secondary school syllabus. I've taught forms 1 until 4 (on odd moments, I taught add maths to form 5s about to take their SPM during form 1 recess time) and I've seen how the syllabus and exam formats have changed over time. I have prepared 3 different formats of English exam papers throughout my years teaching in secondary school (2015-2021).
Now that I'm no longer teaching in school, I find it a bit odd that my students are nurses now, instead of school children. The difference between teaching children and adults is knowing who their audiences are. Adults and children learn differently and this also depends on their profession. What hasn't changed is that I teach to ensure they are able to use the language in life. It's not all about the exams. In that way, they can even do IELTS from doing practice on their own,without even going to specific IELTS prep classes. Believe me, I've done it before - able to get band 7.5 in 2010 and 7.0 in 2019 even though they're in different formats (please invest in the exercise books to know the current format of the exams. It may have changed).
For adults, it's usually concise.Send concise e-mails because your colleague might not have a lot of time to read many paragraphs. Mind you, there may be many e-mails in waiting. Communication also depends on your audience. Is your audience a child, an elderly, a busy person, or someone who may have time to listen to the rest of the speech? Tailor your oral language skills or your e-mail or letters by expecting who will be reading the end product.
Your word choice is an important part also. Don't make it too complicated. Simple is enough.
Remember, English is easy until you make it too complicated to use. Please stop using Manglish where you just literally translate Malay to English and make the English sentence sound like a Malay sentence.
On a side note, I translate Malay to English contextually. Literal translation never works. It may even wrongly translate the message.