Is there any mistake in the sentences ?

Never use more than one exclamation or question mark.

Sure sir. Thank you very much.

First things first: Are there any mistakes in these sentences?

The sentences contain several awkward usages which a native speaker would likely not employ. There is one egregious mistake which I will underline.

Sometimes all of us get lost in our own deep thoughts. There was a man who was a watchman at a washroom somewhere in Kashmir. He was completely absorbed in his own thoughts; thoughts which included all sorts of feelings such as sadness, happiness, worries, grief and many more. I hope whatever thoughts he is lost in will not kill his happiness. Nevertheless, we are all in the same boat; I pray to God for your happiness.

"Ya" is not a word in English.

I can't thank you enough for the corrections . Regards.

It is a filler in spoken English in India, used, often at the end of sentences, in a way akin to the upspeaking heard in Australia/Zealand, and, sadly in Britain more and more. It is roughly equivalent to "you know?" "you get me?" "OK?" etc. Severely non-standard in written English that is not quoted dialogue.

I am keeping both your words in my mind . Hope you will help me in future too. Cheers .

We will be happy to help you. Centrox can advise you best on British usage, and I will be happy to advise you on North American usage. (Although Canadians use British spellings, and sometimes pronunciation, most of their idiomatic expressions they have in common with the Americans--probably as a result of radio and television.)

I am very happy to meet you here . I hope to speak and write better English.