Replacing character inside string pascal
_Dear___friend___I can't__solve_this.Please_____try_to_solve_it.__And__how__are_you_?All_is___good_.

Dear friend I can't solve_this. Please try to solve it. And how are you?All is good.

Function correctMe(sentence: String): String;
BEGIN
  firstChar := sentence[1];
  WriteLn(sentence);
  IF (ord(firstChar) < 65) OR (ord(firstChar) > 90) THEN BEGIN
    Delete(sentence, 1, 1);
    correctMe:=sentence;
  END;

  BEGIN
    FOR i := 1 to Length(sentence) DO
      IF (sentence[i] = '_') THEN BEGIN
        Delete(sentence, i, 1);
      END;
  END;
END;

FOR i := 1 to Length(sentence) DO
  IF (ord(sentence[i]) = 95) THEN BEGIN
    Delete(sentence, i, 1);
  END;
END;

FOR i := 1 to Length(sentence) DO
  IF (Pos('_', sentence[i])) THEN BEGIN
    Delete(sentence, i, 1);
  END;
END;

FOR i := 1 to Length(sentence) DO
  IF (Pos(95, ord(sentence[i]))) THEN BEGIN
    Delete(sentence, i, 1);
  END;
END;

function correctMe(sentence: String): String;
var
  Idx, SentenceLen, Start, Len: Integer;
begin
  correctMe := '';
  sentence := Trim(sentence);
  SentenceLen := Length(sentence);
  If SentenceLen = 0 then Exit;
  idx := 1;
  while Idx <= SentenceLen do
  begin
    if (sentence[Idx] <> '_') then
    begin
      Idx := Idx + 1;
    end else
    begin
      Start := Idx;
      Idx := Idx + 1;
      while (Idx <= SentenceLen) and (sentence[Idx] = '_') do Idx := Idx + 1;
      Len := ((Idx - Start) - 1);
      if (Len > 0) then
      begin
        Delete(sentence, Start, Len);
        SentenceLen := SentenceLen - Len;
      end;
      sentence[Start] := ' ';
      Idx := Start + 1;
    end;
  end;
  correctMe := sentence;
end;

program test;

Function correctMe(sentence: String): String;
  var replacement: String(255);
  var temp: String(255);
  var i: integer;
BEGIN
  temp := ' ';
  replacement := '';
  IF (Pos('_', sentence)) > 0 THEN
  BEGIN
    i:= 1;
    WHILE i <= Length(sentence) DO
    BEGIN
      IF (sentence[i] <> '_') THEN
      BEGIN
        temp[1] := sentence[i];
        replacement := Concat(replacement, temp);
      END
      ELSE
      BEGIN
        temp[1] := ' ';
        replacement := Concat(replacement, temp);
        REPEAT
          i:= i + 1;
        UNTIL (sentence[i] <> '_') OR (i>Length(sentence));
        i:= i-1;
      END;
      i:= i+1;
    END
  END
  ELSE
  BEGIN
    replacement := sentence;
  END;

  correctMe := replacement;
END;

begin
  WriteLn(correctMe("_Dear___friend___I can't__solve_this.Please_____try_to_solve_it.__And__how__are_you"));
end.

function correct(sentence: String) : String;
BEGIN
   for i:= 1 to LENGTH(sentence) Do
      if (sentence[i] = '_') THEN
         sentence[i] := ' ';
end;