In 2016, she started the competition season in Hungary at International Tournament Gracia Fair Cup, where she won gold all-around medal in junior category.

At the International Tournament Alina Cup in Moscow, she won gold in clubs and rope, bronze in hoop and silver in Team competition.

[5] She also competed at International Tournament Baltic Hoop in Riga, Latvia, winning silver medal in Junior all-around.

At the 2016 European Junior Championships in Holon, Harnasko won two silver medals, one in teams (together with Yulia Isachanka and Julia Evchik) and one in the individual hoop final (tied with Israel's Nicol Zelikman).

She then competed at the Senior International tournament in Moscow, the Alina Cup where she finished 4th in the all-around behind Israel's Nicol Zelikman.

From March 31 – April 2, Harnasko competed at the Grand Prix Marbella finishing 9th in the all-around and qualified 2 event finals, where she won bronze in ribbon.

[10] On May 5–7, Harnasko competed at the 2017 Sofia World Cup again finishing 4th in the all-around, she qualified in 3 apparatus finals and won gold in clubs ahead of hometown girl Neviana Vladinova, bronze in ball and placed 7th in ribbon.

On August 4–6, Harnasko competed at the 2017 Minsk World Challenge Cup, winning silver in the all-around behind Aleksandra Soldatova.

On August 30 - September 3, Harnasko and Katsiaryna Halkina represented in the individual competitions for Belarus at the 2017 World Championships in Pesaro, Italy; she qualified in the clubs final and finished in 7th place.

Harnasko started the season at Baltic Hoop in Riga, Latvia where she took 9th place in the all-around and silver medal in the ball final.

[12] She then took silver medal in the all-around at the International Tournament Deriguina Cup in Kyiv and then sat out from competitions for the rest of the season recovering from an ankle surgery, which she had in April.

On May 16-19, Harnasko competed at the 2019 European Championships in Baku, Azerbaijan with her teammates Katsiaryna Halkina and Anastasiia Salos.

On September 16–22, Harnasko, Katsiaryna Halkina and Anastasiia Salos represented Belarus in the individual competition at the 2019 World Championships in Baku, Azerbaijan.

Harnasko competed at Grand Prix Brno and won gold medal in all-around in front of Ukrainian Khrystyna Pohranychna and Bulgarian Boryana Kaleyn with the score of 89,950.

She competed at International Tournament of Marina Lobatch and won gold medal in all-around (105.850) in front of teammate Anastasiia Salos.

[14] In November, she competed at the 2020 European Championships in Kyiv, Ukraine and won silver medal in all-around, tied with Linoy Ashram (100,900) who took gold.

In June, she competed at the European Rhythmic Gymnastics Championships, in Varna, Bulgaria, finishing 6th in the all-around final, behind compatriot, Anastasiia Salos.

Harnasko became the fifth Belarusian rhythmic gymnast to medal at an Olympic Game, after Marina Lobatch (Seoul 1988), Yulia Raskina (Sydney 2000), Inna Zhukova (Beijing 2008) and Liubov Charkashyna (London 2012, being the last).

Harnasko became the first non-Russian gymnast to win a gold medal in an event final at the World Championships since Ukraine's Ganna Rizatdinova in 2013 with the hoop.

In August, she competed at the 2023 CIS Games in her hometown Minsk, where she won the all-around silver medal and received an artistry award from Alina Kabaeva.

[16] On 22-24 March, Harnasko made her first appearance at FIG World Cup series after two years in Palaio Faliro, Athens, Greece.