If you are not sure about your English level, why not take a free placement test online? Perhaps taking one will help you ascertain your knowledge or it will make you realize you need some more practice. Whichever your reasons are, it can serve as a review or as a reminder that we need to keep learning.
You will find the following descritptions for different levels in the tests:
B2 upper intermediate
C1 Effective Operational Proficiency or advanced
C2 Mastery or proficiency
I. 15 questions to check how well you understand English that you read. You obtain a percentage at then end and you can check your level:
II.Oxford University Press – Diagnostic Test: A diagnostic test is a test that helps the teacher and learners identify problems that they have with the language.
Questions by level: https://elt.oup.com/student/practicegrammar/test?cc=pe&selLanguage=en
III. 25 multiple-choice questions. Without time limit:
IV. Check your level with these two level tests: Grammar & vocabulary level test and Listening level test. Questions get easier or harder according to how well you do. If your English is very good you will answer more difficult questions than someone whose English is not as good.
V. The number of questions displayed on the following test depends on your level: