Hello, abiletskyi!
Your current level is Upper-Intermediate, so I prepared a syllabus for the next step (Advanced). Mind these recommendations and may be the determination with you🙂
You`ve stated your goal is achieve C1 level in 1 month. In average it takes 200 hours to process to another stage. Please, mind this volume to plan your studying.
Let`s start with vocabulary as you stated this as your priority.
Step 1. Build your vocabulary as a system
Language words form a structure with its own peculiarities. If you know the origin of the morphology of the word it is more likely that you`ll guess the meaning without translating. To know more how to do it:
379462460-The-Vocabulary-Builder-Workbook-Magoosh-1.pdf
524739687-Norman-Lewis-Word-Power-Made-Easy-Fully-Revised-Expanded-New-Paperback-Edition.pdf
The total (mostly) list of the words of C1 level here:
Step 2. Train correctly
You can create your own https://www.vocabulary.com/ or use printed versions.