Beginner

What to do depends a bit on your goals.
But generally, TIME and EFFORT is more important than pace or distance.
For calorie burn and basic cardio, ride at a pace where talking begins to get difficult but still doable, for as long as possible or at least 45-60 minutes.

For maximal development you need to mix it up a bit. Shorter rides with interval training, longer steady pace rides, casual recovery rides.

Consider getting a heart rate monitor. Do a net search for "bicycle training program".

Pace and distance is only important when you're riding with a group, against the clock, or have a set distance you have to cover.

Apart from being 30Yrs older I am in the same boat as you. When I started I was doing 16km a day, just because it was a convenient round route back to my door. I rode at a pace that sounds remarkably similar to the one described by Dabac above.

As I progressed and my legs felt stronger I increased the distance at the same sort of effort intensity and kept doing so.

Nearly 4 months on I am still doing that every day but now my distance has increased. I did a 70km ride yesterday. I can't do that every day though so for the rest of the week I do either a 40Km at described pace or a 26km at a pace where it becomes harder to try and talk. I use a heart monitor now and my steady pace is 65% maximum heart rate, give or take 5% and I try to stay around 70-75% on the hills, (Like you I live in basically a flat area). For the harder intensity I ride at approx 70% MHR, up to 75%, on the flat and go all out on the slopes. (They act as a mild kind of interval training I guess)

I also ride nearly every day with my wife. She is riding 30km/day most days and her prefered way to ride is basically interval training. Fast then slow all the way.

One important thing to remember is that if your legs are telling you to rest a bit either take a day off or do a low intensity recovery ride. I take 2 rec rides a week as standard and will throw in a full rest day if needed.

I'm 265Lbs by the way.

Learn to enjoy your riding, have fun with it and go as often as possible. And when you feel lazy and don't feel like it go anyway.

I'd suggest time-in-the-saddle is important if your goal is to lose weight and get fitter (along with healthy diet changes - don't forget those - a bike won't fix a [censored] diet!). It takes your body around 20 mins to warm-up, to get into 'sports' cardio mode, so don't go out for 10-15 minute blasts that leave you breathless and imagine you'll lose a ton of weight from it - it's not going to happen and you'll end up disappointed and soon lose interest.

Instead put 45-60 minutes aside three or four times a week and go out and ride. Start off slowly and after 10-20 mins you'll find you warm-up and will naturally find a pace that you are comfortable with (note: you may feel uncomfortable or cold or tired or a bit of nausea for the first 20 mins or so as your body adjusts to the continued requirement to keep everything moving - just ride through it and it should ease off - but if it doesn't ease off, stop, get your breath back, and try again - or quit and try again another day - there's no glory in giving yourself a heart attack over a bike ride! 🙂).

Keep your pace steady and make sure your route is circular so you'll end up back near home at around the end of your ride time. Do make a note of the time and mileage, but don't be ruled by them - just keep them for comparison with what you'll be doing in a few months time (I'm saying don't be ruled by them because they differ from day to day and as you get fitter and lighter they'll plateau naturally anyway; this way you won't end up exhausting yourself "chasing" your previous results).

Once you've got a few weeks under your belt and you're getting used to time in the saddle, think about extending the rides by an extra mile or two, and see how much further you can comfortably ride. It might surprise you how quickly you get used to it and how much farther you can go or how much more time you can spend in the saddle compared to your start-up first few weeks. Alternatively, if you're not in a position to spend more time on the rides, increase the pace a little and see if you can get some extra miles in that way.

The key is to enjoy it. If you focus too much on stats or weight (which fluctuate anyway) it'll take the fun out of it. So long as you enjoy it, you'll benefit from it. 😉

Thanks for sharing your important information. It will be helpful to lot of people

Hey there! Glad you found the info helpful. Always happy to chat about mountain biking and help out fellow riders. If you have any specific questions or need recommendations, let me know. Just remember, it's crucial to be prepared and know your limits out on those trails. Happy riding! ‍♂️