Travelling to Portugal and sicily

Sicily and Portugal do not have any direct flights - the options are via Madrid, London, Barcelona etc. Check out Skyscanner and Rome2rio.com for options. You can fly from Lisbon or Porto to Madeira.

You don't indicate what your interests are or why you have picked these two places, so it is difficult to assist further.

You have left it a little late in looking for accommodation in Sicily in August if your trip is for this year.

Please and thank you also help!

I love Sicily, but it will be very hot in August. This will affect you more if you are planning to use public transportation (and will be waiting for buses outdoors) vs. having an air conditioned rental car. You need to get a guidebook to Sicily; there are far more places to visit than the three you mentioned, and I urge you to see more of the island if you're going to take the trouble to go there.

Madeira is also lovely. In my experience, the weather is moderate in the summer; be prepared for some rain. If you enjoy walking, check out the paths along the levadas (irrigation canals).

I don't think the order of visit mskes much difference in this case unless there are special events you want to see or want to avoid due to their impact on hotel costs. I suggest some Googling on that count.

I suggest you check out easyJet for flights between Sicily and Lisbon. I don't believe there is a non-stop, but there are plenty of flights on that airline serving both cities and the major cities inbetween (such as Paris, Madrid, Barcelona, and others).
In my experience visiting both places last year, the ancient ruins in Sicily are much more extensive and impressive. Both settings have great food, particularly sea food, but the beaches in Portugal are better.
Both places have touristy locations, and both also offer multiple opportunities to visit less touristy sites. My impression is that the west coast of Sicily and the south coast of Portugal are the most visited. The cost of traveling in each place is roughly equivalent.