Arduino nano + Tiny RTC + SIM 800L EVB

I have code like below and i cant make it working, point is i want use RTC to keep date, for send sms with info when system go restart.

Also reading sms to do commands sometimes stucks, and when i send 2nd sms than it do both sms commands at once.

Can some one help me?

code and output from serial in attachment

problems is in this part of code:

void gettime(){
  tmElements_t tm;
  showtime = " ";
  
  if (RTC.read(tm)){
    showtime = "Czas: ";
    showtime += tmYearToCalendar(tm.Year);
    showtime += "/";
    showtime += tm.Month;
    showtime += "/";
    showtime += tm.Day;
    showtime += ", ";
    showtime += tm.Hour;
    showtime += ":";
    showtime += tm.Minute;
    showtime += ":";
    showtime += tm.Second;
    showtime += " .";
  }
  else {
    if (RTC.chipPresent()) {
      showtime = "The DS1307 is stopped.  Please run the SetTime";
    } else {
      showtime = "DS1307 read error!  Please check the circuitry.";
    }
  }
  showtime = "blad RTC!";
}

full code in attachment because was 2 big to quote

serial monitor output

sim800l_rtc.ino (10.7 KB)