Online (or face-to-face) English courses and apps to learn English, based on studying grammar and doing exercises, cannot help you overcome the medium-low level of English.
Why? Because the brain acquires language subconsciously when understanding messages. You need input (listening and reading) appropriate to your level.
Listen to content that you understand enough.
This is well known as «Language Acquisition Theory» whose main exponent is Stephen Krashen, Univ. Southern California. Repeated experiments have proven that listening-focused people not only improve listening as expected, but also their ability to speak and write and progress up to 3 times faster.