I am a beginner at Javascript and I am creating a Pomodoro timer and the buttons are as seen in the image.

When the user clicks on either of the 3 top buttons I want the timer to switch to 25:00, 5:00 or 15:00, respectively. However, when clicked on, the timer initiates. I only want the timer to initiate once the 'start' button is clicked [Problem 1].

Secondly, when the pause button function is called, the timer display stops however it keeps running in the background [Problem 2] and to be honest I have little idea as how to resume the timer from where it was paused - despite searching the internet. Please can someone help me with this, I am really struggling here! Thank you!

var timer = {
  pomodoro: 25,
  longBreak: 15,
  shortBreak: 5
}
var currentTimerType = timer.pomodoro;

function timer_pomodoro() {
   currentTimerType = timer.pomodoro;
   timer_start();
}
function timer_short() {
  currentTimerType = timer.shortBreak;
  timer_start();
}
function timer_long() {
  currentTimerType = timer.longBreak;
  timer_start();
}

var minutesToAdd = 0;

function timer_start() {
  switch(currentTimerType) {
    case timer.pomodoro:
      minutesToAdd=25;
      break;
    case timer.shortBreak:
      minutesToAdd=5;
      break;
    case timer.longBreak:
      minutesToAdd=15;
      break;
  }
  var currentDate = new Date();
  var futureDate = new Date(currentDate.getTime() + minutesToAdd*60000);
  countDownDate = futureDate;
  var now = new Date().getTime();

  document.getElementById('seconds').innerHTML = '00';
  document.getElementById('minutes').innerHTML = minutesToAdd;
  x = setInterval(myTimer, 1000);
}



  function myTimer() {
  var currentDate = new Date();
  var futureDate = new Date(currentDate.getTime() + minutesToAdd*60000);
  var now = new Date().getTime();
  var distance = countDownDate - now;

  var minutes = Math.floor((distance % (1000 * 60 * 60)) / (1000 * 60));
  var seconds = Math.floor((distance % (1000 * 60)) / 1000);

  document.getElementById('seconds').innerHTML = seconds;
  document.getElementById('minutes').innerHTML = minutes;

  if (seconds == 0 & minutes == 0) {
    clearInterval(x);
  }
}

function pause() {
  clearInterval(x);
  }