How do you say 'Thank you for sending flowers to me' in Japanese?

Actually it should not be so difficult to say so for intermediate learners who have passed JLPT N4. But there aren't many people who can say so by natural expressions.

?  あなたは花を私に送りましたから、ありがとう。
Its not common in Japanese to say 「あなた」(you) when situation is clear.

?  花を私に送りましたから、ありがとう。
To tell the reason of your feeling of「ありがとう」, it's better to use 「〜て」 instead of 「〜から」

?  花を私に送って、ありがとう。
Do you remember that 「〜てあげます」when you do something good for others?

?  花を私に送ってあげて、ありがとう。
Wrong usage. When the subject is third person (not 'I' nor 'you'), and when you appreciate what the person do to you, then「〜てくれます」is used.

◯　花を私に送ってくれて、ありがとう。
It might be more natural to omit「私に」, when the situation is clear.

◯　花を送ってくれて、ありがとう。

Final question: How do you say to me in Japanese 'Thank you for teaching Japanese to me'? Hahaha.