Untrue. In 2017, the number of apprehensions at the southern border was 304k. About 20 days in 2017 were Obama days, but for simplicity, we'll give Trump credit for those days. In 2020, the last full year of Trump's term, the number of apprehensions at the southern border was 458k. That's not a reduction.
Your claim oversimplifies the problem. In prior years, the number of "got aways" was estimated to be much higher than in recent years, because of better surveillance and intervention technology and, more importantly, because more people who cross the border illegally in recent years try to get apprehended, instead of trying to evade. Being apprehended allows them to apply for asylum. See
https://www.bloomberg.com/opinion/ar...eaking-records
Furthermore, the number of immigrants living in the US during Trump's term did not decrease as he promised. See
https://www.pewresearch.org/short-re...e-end-of-2023/