php - MySQL searching files by file name, tags, file category and author

I'm doing something like youtube.

How to do searching for file?

My database structure:

Files:

ID (PK)
AuthorID (FK)
Name  varchar
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FileToCategory

ID(PK)
FileID(FK)
CatID(FK)
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TagsToFile

ID(PK)
FileID(FK)
Tag varchar
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1. I would like to let user type something in search textbox and then display him best result according to file name and tags.
2. When user is watching some file I want to show him proposed files list according to file names, tags, category(same as actual file) and author.

How to do that? I would appreciate any code or natural language explanation how to do that.

EDIT

AD. 1

Something like that works but it does not use file name, how to change it?

SELECT f.ID, f.Name, count( t.ID ) AS HowsGood
FROM Files f
LEFT OUTER JOIN TagsToFile t ON f.ID = t.FileID

AND t.Tag
IN (
'lucky', 'wow', 'ninja', 'cat'  -- example of searched words
)
GROUP BY f.ID, f.Nazwa
order by count(t.ID) desc
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