The President of France has many powers, including choosing the Premier, the Cabinet, can dismiss the Premier, dissolve the National Assembly ( once a year) and rule by decree also can declare a state of emergency. He dominates foreign policy and is the " national arbiter" to ensure the security and unity of the State ( Charles de Gaulle used all these powers in his 10 years, thus establishing the precedents and others have followed him).
There is in The France the principle of " cohabitation", when the party in power in the National Assembly is different from that of the President ( Chirac had to work with the Socialists). This forces compromises and has worked in the past, but the President usually want free reins.
The outcome of the election next week is not good for Macron. Many of those who voted for him did so to stop Marine Le Pen. Her support is solid and the only thing stopping her party from winning a large bloc of seats ( especially in the rural areas) is the "deals" to keep her out and some recent scandals with her replacement as leader. The Socialists did not support Macron and they see him as a traitor, so they will do all they can to deny him a majority. The Right are expected to rally around their party too. It will be a four-way contest and the likely outcome is " cohabitation".