the "th" sound as in "think"

I have a hard time pronouncing it

I used to pronounce it like an F, as in false

For example I pronouncing free and three the same way

I have been told that the th phoneme is the same as the Z of spanish, so I switched to it, but to me it sounds slightly different, searching the internet I found a guy who wrote a book and mentioned that only native english speakers or people who had lived for more than ten years in an english speaking country can pronounce "th" correctly.

Do you have any tips?

Is is just me or the vowels in think, thing, thanks are often pronounced rather nasally?

I feel that my th when pronouncing "thieve" is correct , but I feel like I am doing it wrong with think, anything and others

Many speakers of English pronounce TH as T (many NY accents, Manchester), so you'll be understood ;)

"only native english speakers or people who had lived for more than ten years in an english speaking country can pronounce "th" correctly. "

"Basically, the tip of the tongue is placed to the bottom of the front teeth and a puff of air is blown around it."

It's a native sound in Greek, as well.

The "th" sound in "think" is a bitch.

SPANISH SPEAKER: You're in good company - many people in England, supposedly native speakers, and especially in London and Estuary speaking areas, do exactly the same. "Thirty thousand thrushes flew through Thanet on Thursday" " comes out as "Firty fousand frushes flew frough Fanet on Fursday". It's all part of the linguistic scene down there.

But if you want to improve on their standards and speak proper English, practise the "th" sound (in words like "thieve" "thin" "throw" " by making your tongue protrude outwards from between your teeth but not quite allowing your upper teeth to touch your tongue. And then gently blow.

In words like "that" "this" "they" etc the sound is different. Instead of blowing air out of your mouth you just make a humming sound with your vocal chords deep down in your throat. I can't describe it better than that right now as it's the witching hour and I'm ........zzzzzzzzzzz

Actually they have this sound in castillian european spanish . I know it doesn't exist in Latin American spanish versions.