Based on the currency you selected and information I gleaned off your profile I'm assuming that you live in France and want to be able to buy a laptop that could be shipped to France.
Lenovo Laptop IdeaPad 320 €545,99 (MSRP: €720,99) @ Newegg
Features an i7 7th Gen 7500U. If you're not familiar with the Intel lettering system, U signifies that the laptop is a power-saving laptop. Effectively this means that the cpu speed is reduced to achieve longer battery life and energy efficiency. While not breaking any land speed records, will be more than enough for basic coding and internet surfing. Don't expect to run heavy IDEs like Visual Studio without some lag. This option's CPU is about 59.7% slower than option 2 according to it's average cpu passmark benchmark. It also comes with 1 TB HDD and a 256 GB SSD, for a total combined storage far above your requested storage amount. The laptop also features 8 GB DDR4, which you shouldn't come close to filling up in any normal user case scenario. I've even managed to fit in a dedicated graphics card, the NVIDIA GeForce MX150, but that's really gratuitous at this point. You might actually be able to play some really visually intensive 3D games at really low settings.
Acer Laptop Aspire 5 €671,99 (MSRP: €754,99) @ Newegg
The laptop cpu, first of all is an i7 8th Gen 8550 U. The laptop also features 8 GB DDR4. It also comes with 1 TB HDD and a 256 GB SSD. Like option 1 it has a NVIDIA GeForce MX150. You're really paying for the newer, faster CPU at this point.
You should be able to set any laptop to dual boot if you simply install both operating systems on it. I'm assuming you're going for a Linux, Windows set up and this should be very feasible.