It seems maybe the opposition have found out tactically, try something along these lines, with a 4-3-3 but the 4-5-1 style of it, with the holding DM, two CM's, two wingers (in your case inside forwards), and the lone striker.
Full backs - seeing as you will have those wingers most likely cutting in, it's important for your team to have some natural width, which will be given to you by your full backs. Set your full backs to support, therefore they are there to supply an important pass/cross when needed.
Centre backs - they don't need to do anything special, just let them do their jobs as limited defenders, on defend. They can simply pass the ball out wide to the full backs or use the short option of your holding DM which will gradually get the ball forward and avoid any silly mistakes. Think of your DM as your safety net of the team, and therefore needs good concentration, tackling, marking etc.
Defensive Midfielder - as i just said, he's really important for you, because when you have the ball forward, its most likely your full backs will push up to support, along with your centre midfielders, so you must be careful of an opposition counter attack. Put your DM as an anchor man, defend.
Centre midfielders - Seeing as your team seems to be quite attacking, I'd put these as box-to-box midfielders - this way, you'll have more cover defensively as they will track back, and you'll have more support attacking wise which could see you overload the opposition defence with your striker hopefully taking away 1 or 2 markers, your wingers going onto the centre backs aswell because they are cutting in, and then that gives your centre midfielders a bit of freedom in the middle when attacking the opposition defence.
It's also likely that the opposition full backs will follow your inside cutting wingers which leaves space for your full backs to put in a great cross into a crowded box for a good goal scoring opportunity.
Wingers (inside forwards) - these guys are important, because they really have the ability to screw up the oppositions defence. If they have the right attributes like dribbling and off the ball and acceleration, they will pull full backs all over the place and cause real confusion in the box, which could give your strikers/centre midfielders the opportunity to score.
if the opposition decide to ignore your wingers and focus on the runners from midfield and the lone striker, they will probably be punished even more if the quality is there and there will be enough space for your wingers to pick up speed and get a shot in at goal.
therefore, wingers are really quite important in this.
Lone striker - Now, this depends on what type of player your striker is. You could have him in a variety on roles, for example, poacher, deep lying forward, complete forward, advanced forward, or even target man (support) as your wingers/centre midfielders will be there to support him and for him to lay off the ball to them.
personally, from personal experience, if your player is good enough complete forward can be good enough, but only if he's world class tbh (villa, rooney etc), but poacher is a very good option to use. as you have Niang, i think poacher/advanced forward would be good for him.
if you need anymore help, feel free to ask, because that only took about 10 minutes to type up
