Writing a CV is about being concise while also promoting your strengths.
The summary of your professional experience must be:
Your CV must bear your name and a title relating to your career plans or the position you are seeking.
It should specify your academic background, your professional experience through specific details and, if possible, figures: context, objectives, responsibilities, achievements.
Your CV is all about you. Polish the details about your extra-curricular activities: these demonstrate your personal commitment and help to build your experience and shape your personality.
A cover letter provides essential additional details about why you are applying for the position: it goes beyond the CV and is what demonstrates your drive and passion.
Structure your cover letter as follows: a) the company, b) you, c) us! Highlight: a) your interest in the company, its vision, its ambitions, b) what you can bring to it (your experience, your achievements, personal qualities, etc.) and c) what we can accomplish together (your career plans and goals).
Just like the CV, the letter must be clear, coherent, well structured and must not contain any mistakes.