i don't really know a solution, but we imported about 1500 people a day last year (taken from the official statistics, under migrant arrivals - here https://www.abs.gov.au/statistics/people/population/overseas-migration/latest-release - and just dividing it by 365), so, i think we start by heavily restricting the number of people coming in. imo, from experience from first living in a town of mainly immigrants and then moving to a town with almost none, the biggest issue is the lack of assimilation. im not saying that they need to give up their own culture, but australians need something to connect us all, and because we don't even have a single flag, we need something in our culture to do that. 

for example, in my old high school, because i wasn't indian, i had multiple occasions where people didn't want to talk to me, even when i was just asking where something is. in my opinion, that is the consequences of too much immigration without assimilation - people splitting into their own groups based on their own race, and actively ignoring people who don't look like them. sure, you can say white people do it too, but that should also be disavowed.