Disclaimer; I am not a fan of president Buhari. I feel he has harmed rather than helped Nigeria. However, I shall attempt to remain as unbiased as is possible in this Analysis.
With the 2019 elections not being far off and having come accross this article that claims buhari achieved the following things for Nigeria, I wanted to examine how much of it was true.

https://guardian.ng/news/what-buhari-has-achieved-in-three-years-presidency/

His claims summarized are as follows, Gdp went from negative to positive after 5 years of negative growth, inflation fell, agriculture improved, foreign investment increased, stock market performed at its best ever. Power generation nearly doubled, pensions were granted to police officers, Nigeria's ease of doing business rank improved, forex reserves increased, Nigeria successfully issued bonds. It started a tax amnesty program, a social program that allows more kids access to food, created jobs, gave loans to farmers, artisians and traders, reduced food insecurity, nigeria customs service recorded high levels of revenue collection, invested in infrastructure and reduced boko haram deaths.
I used several sources to verify these claims(I cannot verify all because data does not exist for some of the claims). The main sources I used include Trading economics and Wikepedia. Both are good verifiable sources. (Yes, wikepedia can be edited by anyone. However there is a system of constant checks where every edit is checked by multiple contributers to ensure it is correct.)

https://tradingeconomics.com/nigeria/gdp-growth-annual

Gdp fell to its lowest level after buhari assumed power and has currently risen to less than 1/3 its 2014 level and 1/4th its 2010 level. So while the gdp went from negative of 2017 to positive, both were under Buhari.
I don't blame buhari for this one because Nigeria's economy was very oil dependent and it imports most of its consumer goods. A crash in oil was bound to wreck the economy. A recovery from recession in 2 years is not bad.

https://tradingeconomics.com/nigeria/foreign-exchange-reserves

Forex fell from 2013 to 2017 and has now bounced back to its 2013 level. This is impressive but not comparable to the growth of the previous decade.

https://tradingeconomics.com/nigeria/government-debt-to-gdp

Govt debt rose sharply from 2015 to 2017 and did not fall at any point. It also did not fall but stayed stable during the previous govt. It is thus possible that the previous govt squandered the forrex that it claimed to have used to pay off debt. The current government may have borrowed to help stave off the reccession.

https://tradingeconomics.com/nigeria/industrial-production

Industrial production dropped sharply following buhari's taking of office and has now risen but is still far below pre 2015 levels.

https://tradingeconomics.com/nigeria/gdp-from-agriculture

Agriculture has risen but is following a year upon year rise and is not due to Buhari.

https://tradingeconomics.com/nigeria/foreign-direct-investment

Foreign investment fell sharply during Goodluck Jonathan's tenure and has remained low.

https://tradingeconomics.com/nigeria/stock-market

The stock market fell sharply following his appointment (Again possibly due to the crash in oil prices) and has recovered since 2018 reaching pre crash levels

https://tradingeconomics.com/nigeria/inflation-cpi

Inflation rose sharply in 2016 and has been falling since 2018 although it still remains at the highest level since 2010
Power supply appears to have increased although prices have also risen.

https://en.wikipedia.org/wiki/Ease_of_doing_business_index

Nigeria has become easier to do business in following disasterous years where it rose from 94 to 147 (A higher number means it is harder to do business in)

https://tradingeconomics.com/nigeria/unemployment-rate

Unemployment has risen sharply since 2015 and has increased very fast this last year. Buhari has failed here.

https://www.transparency.org/news/feature/corruption_perceptions_index_2017

Nigeria became more corrupt in 2016 than the last decade and then slightly less corrupt in 2017. Overall Buhari has failed to fight or make any significant difference to corruption

https://guardian.ng/business-services/money/the-absolute-sense-of-infrastructure-investments-in-nigeria-2/

According to this report Nigeria is investing in infrastructure which, along with investing in industry is the country's only hope. in 45 years the oil will run out and should Nigeria not dramatically transform, the people will have to go back to farming with no clothes, electronics or other luxuries.

http://www.bbc.com/news/world-africa-42735414
https://www.thecable.ng/path-of-a-ruthless-killer-all-boko-haram-deaths-in-2015

Boko haram deaths declined sharply from 5000 in 2015 to 900 in 2016. However, since then they've slowly been climbing up. Also have emereged groups of fulani militias that have been wrecking havoc. Thus while Buhari did reduce the deaths by boko haram he has failed to adequately increase secrutiy as boko haram deaths are now rising and fulani militias have come about which wreck mass havoc.

All in all Buhari has performed neither significantly worse not any better than the previous governments. However buhari faced what previous govts did not, a massive recession. Given the recession it is difficult to accurately guage his performance and who knows how he would have performed had the recession not occured. However, to those that claim that buhari destroyed Nigeria and to those that claim he saved it. He did neither. Overall his perfomance was pretty bland and is comparable to that of previous governments. While his economic performance is difficult to judge his performance on security and corruption, two of his other campaign promises have been lackluster. Security looked good from 2015 to 2016 but has again worsened and the arrival of fulani militias has again increased the death toll in Nigeria.

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