Ok- so uniquely qualified to comment on this as an auditor.
“In an international audit company” although I would rephrase this bit as not very elegant.
In charge of projects- this doesn’t work in English. Try “project lead” or “Audit Senior” which is the role you describe here. You can change this across the letter.
“In different industries including...”
“I was involved in every stage of the audit: compiling the financial statements...”
If this is for your CV rather than B2 you can say IFRS in a cover letter in audit. You don’t need to type the whole thing out- this is an industry thing.
The next bit doesn’t really work. Try: “as project lead I carried out audit planning, built relationships with clients and concluded on audit findings.” Scrap the next sentence its implied above.
”where I volunteered” “on international projects” “means I am used to working with an international team.”
”Please do not hesitate to contact me if you have any queries.”
Good luck :)