One of my students who is taking the Eiken and the TOEIC tests next month asked me for advice, and I sent her my first reply as follows: (She is aiming at getting the score of over 900 this time.)
You can read quite fast and quite clearly, and I think you can catch the "gist" of what is said when you read in English. However, from what I saw in the sample 〇〇 test, I think you need to carefully understand the details of what is written. Don't you have a tendency to overlook the details?
If you have textbooks to study for Eiken or for TOEIC, study them very well. Study them so hard (repeatedly/carefully) as to learn them by heart.
1. Try the questions in a normal way. 2. Check the answers. 3. Check the reasons why you made mistakes. (Vocab? Grammar? etc.) 4. Read the material slowly and carefully (silently), and check all the words/expressions you don't know or you are not 100% sure of. 5. Learn the material. (Do you understand 100% of what is said?) 6. Read the material out loud. (You should be able to draw pictures of the content in your mind when you read.)