How much can you work out?

You don't need to rest between low-impact cardio exercises unless you feel you need to, but you definitely have to rest between runs. As a beginner, you shouldn't run more than three days a week.

As for the length of time you work out, depending on your goals, it doesn't really matter. For calorie burn, longer at less intensity will get you pretty much the same place as shorter at higher intensity, but shorter will get you there more quickly. :)

You don't need to rest in between cardio workouts unless you feel you need to. The most important thing is to listen to your body. If you feel like you overworked yourself the day before, take a day to rest. If your new to exercise and your body hurts too much after the workout, take a day of rest.

Bunch of questions here. :) I'll do my best to answer clearly.

Yes, you need rest days. Running is a VERY high impact exercise, even on a treadmill, and you shouldn't do it every day. On your non-running days, you need to be strength training to offset the lean tissue loss you'll be getting as you lose weight.

How long you workout doesn't matter; you'll be aiming for the same rate of weight loss whether you work out for 30 minutes or 2 hours. However, if you're like most people, you don't have 2 hours to waste when 30 minutes will give you the same benefit. Running intervals for 30 minutes and burning 200 calories is a better use of your time than running slowly for 2 hours and burning 200 calories.

More is not better; you aim for the same weekly weight loss goal no matter how much you exercise, so the more you burn, the more you eat to compensate and keep from eating too few calories to sustain your activity.

I don't really know if I am doing a good job with my exercising. I recently bought a thread mill and I have been using it for 1 hour and some days 1,5 hour. A few days ago someone told me that you have to rest a day when you run. So run a day and then rest a day. Is that true? And I also wondered if it is better to work out 2 hours but at a lower speed or a half an hour but at a higher speed? Thanks in advance for anyone who answers.