Multi gym workout routine for beginner

Is there anything out there or if you know yourself how to determine how much weight you should be lifting? I'm going for definition, I still have a lot of weight to lose and I know that will help but my main focus is definition.

I recommend to start the first month with only getting back on track in your head. I'm saying that you have to prepare your body for a month for the real training which is going to be after this. This though, doesn't mean that you'll do the bare minimum, you'll also see results and you'll look way more better with your shirt off than you're looking now. I suggest to do like this : In the first week you’ll train all major bodyparts in each workout (as opposed to “splitting up” your training). Train three days this first week, performing just one exercise per bodypart in each session. It’s important that you have a day of rest between each workout to allow your body to recover.
In the second week, you’ll begin to train different bodyparts on different days with a two-day training split (meaning the entire body is trained over the course of two days, rather than one as in the first week). You’ll train a total of four days this week; the split includes two upper-body days (Monday and Thursday) and two lower-body days (Tuesday and Friday), and each bodypart is trained twice. Wednesday, Saturday and Sunday will be your recovery days.
In the third week of the program you'll step it up to a three-day training split: Train all “pushing” bodyparts (chest, shoulders, triceps) on Day 1; hit the “pulling” bodyparts (back, biceps) and abs on Day 2; and work your lower body (quads, glutes, hamstrings, calves) on Day 3. As in Week 2, you train each bodypart twice a week, so you’ll hit the gym six days this week.
In the fourth and final week of the program, you’ll train four days in a four-way split that hits each bodypart just once (except for calves and abs, which are each trained twice). Four-day splits are common among experienced lifters because they involve training fewer bodyparts (typically 2–3) per workout, which gives each muscle group ample attention and allows you to train with higher volume. As you’ll see, chest and triceps are paired up, as are back with biceps and quads with hamstrings, each a very common pairing among novice and advanced bodybuilders. Shoulders are trained more or less on their own, and you’ll alternate hitting calves and abs—which respond well to being trained multiple times per week—every other workout. No new exercises are introduced in Week 4 so that you can focus on intensity in your workouts instead of learning new movements.
Once you complete this little program, you can start add more reps and new exercises. This little program is just a preparation for the heavy workout you'll do in the next weeks.
Hope I was clear enough ! Good Luck mate )