"Many thanks for your kind wishes and supportive words i really do appreciate them." -> "Many thanks for your kind wishes and supportive words. I really do appreciate them."
These are two independent clauses; use a semicolon or a period here.
"I will never hesitate to contact you when need help." -> "I won't hesitate to contact you if I need help."
'will never' seems too definite and imposing. We use 'if' instead of help, because we don't look forward to needing help.
"This email address is my personal one and you can keep using it to contact me." -> "This email is my personal one. You can keep using it to contact me."
Try to avoid run on sentences. Separating these sentences makes them more comfortable to read.
"After 13 th February (my flight date) I will be in Düsseldorf Germany and waiting with patience to hear from you." -> "After the 13th of February, my flight date, I will be in Düsseldorf, Germany, waiting with patience to hear form you."
You can say "13 February" or "the 13th of February", although the latter is much more common in American English.
"my flight date" is important context for the sentence, so don't put it in parentheses. Anything in parentheses should be details that could be ignored without compromising the sentence.
Again, the use of 'and' can tend to make sentences feel long and awkward.