Welcome to the forum. Sorry you've gotten this diagnosis but the good news is that your condition is treatable and with knowledge and experience I'm hopeful you'll get it under good control.
You have a lot of questions, which is great. Let me take a stab at them.
1. That to do with the pain as NSAIDS ar bad for us?
DO NOT TAKE NSAIDs.2. Before diagnosis and starting medicines I had rectal pain and it was difficult even to sit, it is almost gone now but it comes beck with my monthly period (for first couple days) and I do not know how to deal with this. Any advices from who experienced rectal pain?
Many women have this experience. It should diminish as you get better control over the inflammation. You might consider using birth control pills in the near term to limit your hormonal cycles while you get over this flare.
3. I put myself on gluten free, sugar free, low fat, dairy free diet and I think this helps a bit with the pain. Also started probiotics (I still do not know what kind it should be and in drug store they do not know what to suggest for UC) also Turmeric, Folic acid, Omega 3, regular vitamins. I have no diarrhea, no anemia so isn’t that too much? "Too much" is subjective. I personally avoid a lot of supplements, and since all of this is new to you I think it will be hard for you to tell what is working and what is not working when you are adding so many things all at once. However, I understand your desire for quick results. Your list looks good, with the possible exception of "regular vitamins." I don't know what that means. If you are eating a healthy balanced diet you don't need vitamins. You do probably need vitamin D and I would ask your DR to test your levels of this specific vitamin.
4. I started exercising- running is best for me, I do 6 to 10 km every second day but I noticed that sometimes I get pain in my lower back and a my abdomen hurts more- can it be from UC? I was always athletic, live actively- love hiking, bicycles (stopped this because rectal pain), swimming, skiing and never had any pain during/ after any activities. Yes, lower back pain is common with UC.
5. Me and my husband would love to have our first baby, my gynecologist says nothing about UC drug influence to fetus and I do not know what to think. the medication you've been given is not absorbed and is safe to use during pregnancy.
6. I do not know if I’m in remission should it be symptoms free or what. My health improved greatly only with diet change and Salofalk enema but I still have mucus in stool and some abdomen pain. remission should make everything normal. No blood, no mucous. rectal inflammation is very stubborn and it will take a while to get rid of it.
7. I ‘m doing quite good with Salofalk but do not know f it’s safe to use them for long time should I as for oral medicine as well. oral mesalamine will probably help you get better faster. The rectal meds are the best for what you have. You should plan on using rectal meds plus an oral mesalamine for a very long time to maintain a remission. The length of the prescription you've been given is not sufficient.