It seems there are multiple things here that need to be touched up on. I may not consider myself the best DM but I've been writing modules up since my dad introduced me to Advanced Dungeons & Dragons when I was 10 and running them since I was in high school... so maybe I can help?
First off, if you're bringing in new people...always play for a shorter amount of time or if you want to bait them lie to them. I know this sounds like it sucks, but I have come to notice over the years that when I focus peoples attention on the amount of time we'll be playing for they tend to freak out and not enjoy the game. Instead, say you'll probably play for about two or three, this will make them feel more comfortable, like they are testing the waters. They'll hopefully feel more focused on having fun and when the hours all of a sudden go by, and you've made things interesting, they'll hopefully beg to stay and play a bit longer...if they don't ask for more time offer it, if they seem hesitant to take it because they have "things to do" it is sadly time to look for more players.
When it comes to timing and moving things along, you need to be the one to push them along. If they are chatting outside of game, get them refocused. My favorite thing to do is tell my players that for every time they get off task I will minus EXP. The first couple of times you do it, but then you just say it, and then hopefully they stop talking ridiculous amounts outside of character like they eventually did with my group.
If they are sitting in a room and won't move and an HOUR literally goes by...it's really time to throw a strong encounter in to get them moving or have something happen. One time I had a party who thought they beat a thief up a mountain, but they didn't and they were just camping out in a cave system. To freak them out further up the mountain, I "Rolled" a random encounter and had them hear the cry of a Wendigo. That brings me to another point, if things are getting a bit stale feel free to deviate from your module, no one likes a stale story and if not enough is happening then the players will get bored.
When it comes to combat I strongly suggest having your new players make combat notes. They take the time to write out all dice they roll, so like "To swing longsword: Roll a 1d20+5 on hit roll 1d8+3," etcetera etcetera. There is a space for this on their character sheet, but some people do get taken back by all the information on the sheet. For smaller battles if things are going a bit slow but it is because they are planning too much, slightly insist or hint that the battle doesn't need this much planning. If they are planing for a hard battle and things are taking a bit of time between turns, that sadly is what happens. No one wants to die to a dragons breathe, so players will always question their teammates before diving into a tough fight.
When it comes to getting people together, sadly there's no changing that. With my group it took me a good month to settle in a good day for us all to play and get around work schedules and school. If the people can't make it, I strongly suggest you reach out and find more people willing to play.
