1. "When should I workout?"
Trabelsi and colleagues (2013) found that bodybuilders who weight trained at the end of a fast during Ramadan saw no impact on body composition when compared to those who trained fed. Both groups also maintained their training volume and didn't report changes in how difficult the sessions felt. This can be largely explained by the hormonal response to fasting. So, you can be re-assured that when you train will have little impact on your results.
However, you may find that training at a specific time of day suits YOU best. Training just after you begin your fast may make the session more manageable, but will prolong the fatigue through your fast. On the flip side (and what I would recommend) training just before sunset makes the day more manageable, the session a little more gruelling, but you can seek comfort knowing you break your fast afterwards.
2. "How should I break my fast?"
Put yourself in the shoes of your gut. What would you find most manageable after a period of rest... foods that are easily digestible, in moderate quantities. There will be a natural urge to "let the flood gates open" as the reward centres in your brain turn to food as a reward for abstaining from it. In addition, this is your "chance to eat", but you must be wary of taking on too much too soon.
Start off slow, and seek foods that are calorie dense, lower in volume, with moderate fibre. You can also "prime" your digestive system before a larger meal, by adding two tablespoons of apple cider vinegar, a splash of lemon or lime juice and some water (or sparkling water) to a cup and sipping before the meal. I would also recommend taking digestive enzymes to support the digestion process.
3. "What to eat in the morning? What foods will keep me full?"
Avoid consuming meals that are rapidly digested and high in sugar, like a bowl of cereal with a glass of juice. This will spike insulin, make you crave more carbs, and won't hang around for very long. Instead, consume whole grains such as oatmeal, whole grain bread, quinoa, vegetables and legumes. Combine this with a good portion of protein, as protein is highly satiating (filling) - also to ensure you meet your protein requirements.
Lastly, and most importantly, HEALTHY FATS. Not only are fats highly satiating (filling), they also contain 9 calories per gram (as oppose to 4 calories for carbs and protein) making them calorie dense. They also slow the absorption of glucose into the bloodstream. So, for example, protein oatmeal topped with nuts and seeds, peanut butter, dark chocolate, a banana, and coconut oil.
4. "How to lose weight during this period?"
Those bodybuilders who trained fasted during Ramadan saw a 6.2% decrease in fat mass, whilst the fed group lost no fat mass. This is due to the ease of finding a calorie deficit when training fasted (as it dissipates hunger in a period where you are usually the most hungry). Further steps can be taken to reduce your calorie intake, like eating high volume low calorie dense foods - I wouldn't advise this as you are already limiting your food intake. Just don't over eat.
5. "How to maintain/gain weight during this period?"
Consume calorie dense foods that are low in volume. Specifically, healthy fats. Avocados, nuts and seeds, nut butters, fattier cuts of halal meet, cheese, oily fish (again, if halal), eggs, full fat yogurt, oils (uncooked olive, coconut, etc.). You also want to seek easily digestible foods, moderate your fibre intake, and cosy up to a BLENDER. Smoothies are a great way to increase calories (get those fats in) - they also break up fibre in foods.