read about these 2 methods and class on different sites. With CONVERT everything is clear, but with 2-methods related complexity and what are their differences?

Answer 1, Authority 100%

int.parse (String S) method tries to get the number from its string view, if successful returns the number, otherwise throws formatexception .

int.tryparse (String S, Out int Result) checks whether it is possible to get a number from a string. If possible, returns True and the obtained number OUT -AMER, otherwise returns false result and Default (int) Out -pameter.

This is if it is simple, other exceptions can be emitted, depending on what the string you pass.

Example of using the second method:

string s = console.ReadLine ();
if (int.tryparse (S, Out int i))
  Console.Writeline ("Number, increased by 5: {0}", I + 5);
ELSE.
  Console.Writeline ("The introduced string was not number.");