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Sterilizing soil in large quantities for a home gardener can be difficult.

Here is a link with more information on sterilizing soil.

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/sterilizing-soil.htm
https://www.gardeningknowhow.com/garden-how-to/projects/how-to-solarize-garden-beds-to-eliminate-garden-pests-in-the-soil.htm

It is certainly possible (and unfortunate) that an herbicide may have been used on this soil. Manure will not neutralize herbicides, but some (including atrazine) will degrade over the course of a few months or a few years. Others take longer to break down.

Is there a way to find out more details on what herbicide may have been used? This will help you determine whether you can wait till it breaks down or whether you will need to remove the soil.

It's unfortunate that the lawn care company damaged your garden. Would it be possible to contact the lawn care company and find out what chemical(s) they used? The reason is that some herbicides (weed killers) break down in just a few weeks, while others can remain in soil for years. Once you know the chemical name, you can look up product information on how long it takes to breaks down. If it turns out to be a persistent one, you will probably need to replace with new soil.

This advice is aimed toward farmers, but should apply to gardeners as well:

http://oregonstate.edu/dept/nursery-weeds/feature_articles/herbicide_carryover/herbicide_carryover.htm

To see if the soil is safe next summer, you could try the "bioassay" technique they suggest.

Here is a link on amending clay soil.

https://www.gardeningknowhow.com/special/organic/how-to-easily-improve-your-clay-soil.htm

These articles explain how to supplement copper. Copper can be toxic to plants in excessive amounts, so only apply the required amounts:

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/copper-for-the-garden.htm
http://www.extension.umn.edu/agriculture/nutrient-management/micronutrients/copper-for-crop-production/

Nickel is an essential nutrient for plants but is required in very small amounts. Supplementation with nickel is usually not needed, and excessive amounts are toxic to plants. However, if the soil pH is too high, plants can have trouble taking up nickel, so the recommended treatment is to lower the pH to the plant's ideal pH range:

http://www.agprofessional.com/news/nickel-plant-nutrient-%E2%80%A6-really

1/3 sand and 2/3 soil (whatever basic soil you have) is a typical mix. This article gives a great overview of some more elaborate possibilities:
http://www.junglemusic.net/palmadvice/palms-potting-soil-for-palms.htm

Also see this article about palm fertilization:
http://edis.ifas.ufl.edu/ep262