Increasing the amount of a reactant will move the reaction in the forward direction as long as there is sufficient material for it to react with.
If you think about a chemical reaction equation like a balance, or “see-saw”, the driving force” is always to keep the two “sides” balanced (including other parameters – it is not always a linear algebraic balance).
So, if you ADD something to one side, the reaction will shift forward or backwards to restore the “equilibrium” or balance of the overall reaction. Adding additional reactants moves it forward, to produce more products.
Removing products will also induce the reaction to proceed forward again to a new balance point. ADDING additional product material to a reaction will shift the reaction backwards, forming more of the reactants, if thermodynamically possible. Removing excess reactant from a solution may also shift the reaction backwards, forming more of the reactants and reducing the amount of products, if thermodynamically possible.
“Thermodynamics” is one of those other parameters I mentioned that means that SOME things will not easily shift the reaction backwards by a simple balance of the materials. Additional energy resources would also be required.