Welcome to a portion of my past experience of using Deca durabolin(Nandrolone Decanoate)
I'm not going to give definitions on compounds since you should damn well know what they are by now.

Deca has such a stigma surrounding it I compare it to the Gun debate of the current day. The conversation is being steered by the folks who aren't truly qualified to lead that argument. Yes both are dangerous when used unresponsibly both when used with safety and maturity they are quite safe and in the end extremely beneficial to the user.

I first used Deca about 4yrs ago. Cycle was this:
Test Cyp 400mg wk/ 8wks
Deca 500mg wk/ 8 wks.

Little research was done as I was told I'd blow up. That was all that mattered to me. End result was a bunch of water, some and loss of libido after cycle and little to no permanent gains. You see Deca is a longer of an ester and by the time the strength was picking up I was coming off cycle. End result was bloated face and feet, zero libido post cycle and a lot of disappointment.

I knew something didn't go right so I hit the internet. Looked up as many threads on Deca as possible and found a few interesting things.
1) Test and Deca are synergistic but run at a ratio of 2:1 for Test to Deca
2) Protein synthesis is Deca's claim to fame along with huge amounts of strength.
3) Along with Protein, Collagen synthesis is another of Deca's most notorious byproducts
4) CABERGOLINE!
I read that there was a way to run the deca along with Test to help prevent the libido issues. Run Testosterone 2x higher than Deca as the Deca attacks the reproductive system and all the surrounding fucntions like libido and good errections due to the 19nor aspect. How it triggers progesterone and how that will fuck your best Pornstar abilities like nothing else.
I read about eating enough Protein to maximize the Protein synthesis abailities of Deca.
Collagen was new to me. I read about it and always had wondered why when I used winny(Which was the easiest compound for me to get) my joints killed me and especially my shoulders and knees. I read that at low doses people got just enough relief from the Deca that they would run low doses on cycle regardless of if Deca was a centerpiece of the cycle or not. They'd run it just for relief. I loved that part.
Then the answer to the majority of all my questions appeared. Cabergoline(Dostinex) or other similar Prolactin Inhibitors like Prami/Bromo are how a real Deca cycle is ran without ever having horrible humiliating sexual dysfunction. Most guys who have experienced this knows how emabarrassing this is and I myself vowed to never let it happen again.
So I took what I learned and made some adjustments. Here was my second Deca cycle:
Test 600mg wks 1-12
Deca 300mg wks 1-12
Test Prop100mg wks 13-14
Adex .5mg wks 4-14
Caber .5mg 2x wk 5-12( I waited 4 wks in to use since my ed issues happend wks 6-7
Results were a lot better strength wise The Deca seemed to lean me out alot. Adex worked on any bloat but dried me a little too much in the joints. The Caber was too strong. I was a walking raging sperm fondue. But post cycle the ed stuff came back. WTF!
I PCT'd hard and after 10 wks I was back to normal. Research showed me that Guys were running Caber into the first couple of weeks into PCT to help any ED sides. Decided I would do it that way next.
Maybe a year went by and I was ready for more. My goals were to add size and power this cycle.
Cycle was;
Sust 750 wk wks 1-12
Deca 400mg wk 1-12
Drol 75mg daily wks 1-4
Test P 100mg 13-15
Adex .25mg wks 4-15
Caber .25 daily wks 5-17
(Also decided to add HCG for any shutdown problems and for aerodynamics)
HCG 250iu 2x weekly starting at first sign of shrinkage which was around wk 6
End results was the best Deca cycle I had ever had up to that point. The power from the Drol was amazing. Headaches sucked ass and BP was an issue. By the time the drol effect ran out I had Sust kick in and by week 8 the Deca was hitting hard. I gained nearly 30lbs and by the end of the PCT I held on to 20lbs of it. No ED issues or lack of libido during cycle and during PCT. I truly felt I was on to something.
I have done two more Deca cycles since but maily with NPP kickers and Tapers. Bigger dosages and different AI's inclusion of HGH and longer more complex cycle structure.
A user can learn from the mistakes of others but I didn't really get that chance. I learned these things on my own:
1) Prep time. Planning of goals. Purchasing enough Gear,AI, Caber, HCG, PCT, Protein, Getting in my case BPmeds ready. Training and Diet regimen dialed in at least a month ahead of cycle to see if goals can and will be met using that system
2) Protein needs to be at 350g-400g to see the real magic happen. Intensity will go up regardless so make sure your Carb intake supports your training times, otherwise you wont maximize your energy to support the intensity increase.
3) Collagen is your friend and if given the opportunity Deca can be used at a very light therapuetic dose like 150-200mg to allieviate Joint stress and discomfort.
4) Any and all Deca cycles should include Caber or another Prolactin Inhibitor. A low dose of .25mg is more of a preventative dose. .5mg is more of a dose if you already have sides present. Run it 2 wks into PCT or as blood tests indicate a need.
Deca is one of the most versatile Compounds ever made. It's famous for tremendous Power increases, mass building. It can also be used at a modest dose of 250-300-350mg to get leaner gains. Or if the years of heavy lifting or hardcore competition dry out has left a toll a user can use a low therapeutic dose of 150-200mg or according to personal preference.
Please do not ask me to write you a cycle. I am speaking on personal experience exclusively. Through trial and error I learned my way. Some may want to write your cycles for you but I will not